Newbie with "Sipper" a sweet 2007 -- but not-sweet 12V

Hi : ) I'm Elly and I live in Nanaimo, BC, Canada. Even though this must be the banana belt of Canada, we do get Winters, often with snow, always with freezing temps, ice, salt. Sometimes floods. It can get hot in the Summers, too. Not easy on vehicles ... Especially batteries.
A year and a half ago, from the same auto dealer I bought my previous car, I purchased a not fancy but very clean and sweet 2007 which, I think must be a 2nd generation. (?) Unlike the car I traded in (3 extra keys) it came without a spare key, just one single key fob (with door key inside). Apparently it's next to impossible to get another, at best ridiculously expensive. So that aspect causes me some concern.
There is no extra button on the door handle, so I think it must not be a Smart Key model. I understand this is important when it comes time to replace the 12V battery, possibly among other things.
I am delighted with the car, but didn't drive it very much and then, thanks Covid, got locked down. The car had some weird little things happen before we both got grounded. Just a few trips out, and then she wouldn't start. A jump start got her going, but she wouldn't hold a charge. When the trouble first started, I tried to replace the battery, and that was the start of some major stress and unsuccessful efforts that resulted in the car sitting for weeks over the Winter : ( While I was down sick, though luckily not with C19.
Now, I have been trying to get her going but having the same trouble I did at the start. I cannot get a battery to fit ! Back on my first try, the battery shop wanted to put in a Delco ACDB24R which they assured me had gone into several other Priuses Pris ? But it was too big (wide/long.)
This time, a different place assured me they had one to fit and even brought it to my home. Turns out it is the same battery, so it had to go back.
We have all kinds of shopping here, but what we lack is any choice of Prius car batteries ! And getting anything shipped? Well, good luck with the cost of that. I've been getting by mostly thanks to Amazon, but over $500 for a battery ? Plus, they don't even ship beer . . . Yeh, poor me. A dead Sipper and not even any beer in the house.
When I phoned the Toyota service department, I was told there is only one battery for my car and that theirs will fit. He said that maybe someone had done a modification on the car for the current battery.
So, having been through this twice, I know that the Delco is larger than dead one. If Toyota's is the same size, it will not fit. Therefore, there must at least be 2 sizes. Right?
I did phone the company whose name is on the current battery but they are a wholesaler and don't have a dealer near here... grrrr. So I cannot replace with a duplicate. Also, since I had troubles so soon after purchase (in the Summertime) and the date on that battery is 2019, I wonder if it would be a sensible choice anyway.
Plus, there is this Smart Key question. YouTube vids usually talk about Smart Key cars but mine is a base model. They tell which battery to get for SK models and said their video wouldn't work for others. Why? I don't know. So I don't know if it would be safe to install the Delco, even if it would fit.
I cannot believe this is so difficult.
Last night it occurred to me that maybe someone did do a modification in the battery well so a smaller battery would sit securely. Why? No clue. But, what else could it be? So I took a look inside and there is a metal thingy in there which is why the base of the Delco won't sit flat. There is ample room at the top, but not on the floor.
Now that it's daylight, I will go take photos of the battery well and try to figure out how to post them.
But first, I thought I'd write and introduce myself.
I can certainly see why people are so in love with these cars. And, to heck with Covid. If I can get "Sipper" running, I will be very relieved, and promise to take her out for a run every few days. Just me and the dogs. Going nowhere. Wasting gas, causing pollution for no reason. Except to keep us running -- and sane. Neither of is thriving any more while I'm doing solitary ... (and, without even having committed a crime ; )
I am glad to have found this forum and will be very grateful for any suggestions and help.
Cheers! And, Stay Safe.
Elly and Sipper

 

On digging further into this site, I found a link to a Toyota Parts Chart explaining their batteries. Yesterday the service department told me there was only one size of battery. But the chat post and Parts Chart show two. This leaves me with little faith in our local Toyota service department, so I am continuing my search. My 2007 (non Smart Key) probably needs the smaller S34B20R. However, it's not that simple either because there is a little 1, so I found the note on the bottom of the page and it says, "TrueStart only." I'm not sure what that means, nor what to do with this new information. I did phone a battery shop but these new numbers did not come up with anything.
I'll post a screen shot of the chart.