P0442 error mechanic says $700 fix didn't give me the parts number and I can't find them anywhere online

• Engine light went on earlier this month.
• Went to autozone where they got error code P0442.
• Later in the week I went to the mechanic because gas seemed like it was disappearing from the tank. Putting in 1-3 gallons a day because it kept saying low fuel even after I filled the tank 1/2 way the day before. (I drive around 16 miles a day).
• Mechanic scheduled an evap smoke test to see where the leak was ($149). Said it was in the Evap pressure sensor hose but I should probably change the whole evap system out since it's getting old if I want to.
• Shows me a picture of the youtube video and says I would need to get that if I wanted to change the whole system out. The picture is for another type of car and he doesn't give me the parts number to that or the hose.
• I tell him it's a lot of money and I'll need to find a way to get it before making an appointment.
• He tells me I can get the parts myself to save on his upcharge.
• Try to look the parts up online but the seals say they're not compatible with my car
• Spent around a day looking for the evap pressure hose sensor system but I don't think anyone sells it anymore (just the sensor). (if I need to change out the whole thing I'd rather spend a couple hundred more now then have them charge $500 in labor down the road to change it because I just got the evap pressure sensor hose swapped instead of all of it.) But I can't find the whole system or product number when looking at car diagrams.

I don't know what to do. Please tell me if this all seems legit or not? Should I just trust him and let him get the parts so I'm not personally getting the wrong ones? Or spend another couple hundred to get a second opinion?