Greetings, maker of stuff. Welcome to Geekhack, place for fellow makers of stuff.
The
Classifieds section is where you'll want to look for something you can't find in stock anywhere.
You won't be able to post there until something like 25 posts and 2 months membership, however. I imagine that's to hopefully deter those who may be joining with nefarious aims. You could PM somebody that's selling though.
MechMarket is another place to look.
Good luck.