Check out nfl auction.
It is run by the NFL and most of the teams sell a lot of items, especially during the season.
They have a lot of footballs and mini helmets, and a few full sized helmets and game worn gear.
A lot of the pink equipment that you see during the breast cancer awearness month ends up on this site.
I managed to get a logan mankins signed pink game used shoe.
If you bid during the season, prices can get very expensive.
But if you hold off to after the draft when things are quiet you can get some real bargins.
I have managed to get signed footballs of jerod mayo, vince wilfork and vincet jackson all for under $100 dlvd each.