I have seen kits on Ebay with those brackets. That might be the best way to go. Only thing is I think those brackets have to be recessed in pockets down into the floor for the seat to lock in place properly.
I just though maybe someone had cut the factory bracketry off and came up with another way of doing it. I didn't want to be the first one to cut the fabric off the bottom of my seat only to find a can of worms underneath.
