Best temporary fix for a dead rear wiper blade?

What about an Automotive Parts store?

 

Not being facetious, but consider not using the rear wiper. If you can get up to ~50mph the rear window clears itself with the slipstream. Outside of Toyota, there's not much in the compatible market over here.

 

I say this without having done it on Gen 4, but what I would try (and have done with past Prius) is take the wiper arm off the car and carry it into a parts store and find a match

 

Just go to Autozone or equivalent and tell them what you want. They'll look it up. If you ask, lots of times they will even install it for you

But I also echo the "just don't use it" comment.... there's really no need for a rear wiper on a sedan. Some models don't even have one. Mine doesn't. It never even gets bad enough that I'd ever use one, even if I had one to use

 

I assume you need part 6 or 7 in this diagram. This dealer sells online. I have ordered parts from them in the past.

2016 Toyota Prius Parts - metrotoyotapartsnow.com

 

You could put some Rain-X or similar water repellent on the rear screen.

 

Amazon also has them. Because of the issue I had with getting replacements for the front, I bought a spare rear one. I believe it's Bosch and it matches perfectly.

Bosch Rear Wiper Blade H409 /3397011431 Original Equipment Replacement- 16" (Pack of 1)

 

Not Amazon.co.uk though, sadly!