AliExpress and Ebay is certainly an option if you want to keep the stockpile yourself

.
Ham fests/auctions, or joining local electronic oriented clubs can be an interesting option as well, if you 'only' need a single (+ a few to blow up) item, for your prototype needs.
Beware that most of the stuff out there are mostly second hand, through hole and 'old tech' (No 0402 smd, fast flash micros, huge eeproms, etc).
Ham operators gone 'silent key' (dead&burried) can also be a good source, and huge caches of components can be had for no price for just carrying it all away, to relatives wanting outrageous prices - depending on relations, etc. Be aware
Polyfuses are extremly usefull and recommended, when you start working on stuff and find that not everything wants to play as you want

Getting a decent workshop takes a LONG time - and a
lot of work. Happy hunting - sometimes gold awaits around the corner (and yeah - it's literally gold plated

) you just have to find it.