2011 Code P0441 P0455 major leak, major issues? canister replacement?

Hey kids, so I've got a 2011 with 250K miles on it. suddenly throwing the dreaded P0441 P0455 codes which most of the time are a missing gas cap error, but eeegads I've been though it. I've checked, double checked and replaced the damn cap. Thats not it. I've tested the purge solenoid, the one by the exhaust manifold, it's good. Next is the canister itself which is a $500 part! Now, the university of YouTube has several videos discussing canisters and how to test them or replace certain components but NONE specific to the Gen3 Prius. does anyone have any procedures or pointers on the Gen3, or do I just bit the bullet and replace the damn thing?

thanks all