I used to buy things from MCM Electronics waaay back in the day but they've turned into something completely different. On a per piece basis ebay kits are a little expensive but you get the kit, instructions, and tons of feedback on how it works. There's a lot to think about when choosing the correct capacitor, not just rating but material too. I picked up a cap at Radio Shack once to fix some handheld (gamegear maybe) and it worked but you got some popping and hissing at higher volume. I found out years later the dielectric matters not just capacitance.
There's lists posted everywhere (here's one https://console5.com/wiki/Turbo_Express
If you want to go piece by piece amazon works well (I don't know any specialty sight anymore that's cheap and easy to navigate) but I don't think you'll be saving money until you're working on multiple units.