http://www.titleboxing.com/

These guys are about the cheapest i've found. They have 15 dollar boxing gloves and shin pads. I use them myself for MMA sparring and they're just fine. Head gear is a little harder to come by for cheap, but it's out there, although i recommend spending a little extra on Revgear's model. I don't know anything about those groin guards, other than they make it a little harder to kick. I just use a cup.