I've built a few rigs over the last few months, and I got tired of swapping my 501PL plates around. Frustrated, today I decided to grab a few more spares so I don't need to rotate them (and I always seem to lose them). Here's a listing for generic 501PL plates for just $9 dollars + FREE SHIPPING in case you guys need some.

Manfrotto 501PL Compatible Quick Release Plates