[QUAD-L] Slot Nuts

[greg]

You know the little slots on the side on the chairs back, or seat pan. So you can slide brackets on and screw things to it. I think they are called Slot Nuts. I can find T shaped ones, but I need square or rectangled ones. Anyone know where to buy these? I need like a 1/4 inch thread, about 3/4 wide. Thanks much, Greg