Typically what is used to attach things to a T-Rail system is the male piece which fits the slot, and has holes drilled in it. The holes have bolts that have had the heads cut or actual T shaped heads allowing them to slip into the slot.

You can get around all this by making your own T head shaped bolts, getting lucky and finding them somewhere or by using a hole saw to introduce an area to use round bolts. Basically once you see how you can attach stuff the T-Rail system and you are somewhat resources, which it sounds like you are, you can fabricate a ton of useful stuff to work in the T-Rail system.

The stock lengths of the t-rail material are hard to find. I'll see what I can do.