I believe a rodent chewed through one of my windshield washer tubes (supplying the driver side). I tried following the tube from the reservoir but it ducks behind a panel under the hood. Any ideas on how to fix/replace this tube? Thank you!
You can just put good quality heat shrink tubing that has glue in it over the break. I have done that many times (not on a Prius) and newer had any problem. Just clean it good underneath the tubing and use at least 5cm or 2” peace of correct diameter heat shrink tubing.
In case the break in the line is hidden from the OP's view - tug on the tube where you can grab it, and see if you can feel the tug on the other end of the tube as it exits from the fender to run up to the inside of the hood. If you can, then cut the tube at one end, securely tape a length of new tube to it, and pull the old tube and new tube through to the other side. Then you can use plastic fittings at both ends to attach the new hose to the remaining old hose - or attach the new hose to the reservoir pump outlet if you can reach it, etc.
if you pull on the tube, and it comes out, you'll need to find out what has to be removed to get access to it.
Probably the right front fender... I don't recall seeing the tube when I replaced the right front fender plastic liner on the 2004 - but then I wasn't looking for it, either.