Is it my water pump going bad or is it my headgasket thats bad

I have a 2011 Toyota Prius with 222k miles. Its been running great however I've noticed a couple months ago that the coolant and the inverter reservoir was low. I topped it with 50/50 pre mix from my local Toyota dealer and the level did not go down. I have been checking my coolant level and oil level weekly and my coolant level did not go down and there was no coolant in the oil. However when I checked it last week the coolant level was low. I topped it off and checked it again today and it was low again. Wondering if its possible its the water pump going bad or if I do indeed have a bad head gasket and if anyone has any recommendations on where to get it fixed in Southern California.

I got a quote from Hybrid 911 and plan on visiting them tomorrow to confirm however they wanted 2700 to put a motor in it and I'm not sure I want to put another 2700 into the car after putting a hybrid battery last year. The last thing I want is to put a motor in it and then have transmission issues.

 

No coolant in the oil and no white smoke.
I've looked underneath for leaks but haven't spotted any.
And thats what I was thinking if I do have to get a new motor for it maybe just try selling it for parts instead. It does have some cosmetic damage to.

I'm also curious as to why it seems like to fix the head gasket on the Prius seems to cost more than regular vehicle. I got the head gasket fixed on a 2000 Tacoma I used to have for 1500.

 

I type that wrong. Both the coolant reservoir and the inverter coolant was low. The inverter coolant hasn’t gone down since I topped it off just the coolant reservoir.