craftgrrl | Need help finding adjustable strap hardware

Recently the one store in my city that carried purse-strap hardware/sliders closed down/moved/whatever. I used these sliders [don't know the technical name, if there is one at all] on my purses, and since this is my business it's kind of uhm...imperitive that I find them.

They're rectangular and plastic, with a bar in the middle - exactly the same as the little sliders on bra straps. The ones I got were plain glossy plastic with no company or brand name and I have yet to find another store that carries them or even knows what they're called.

Does anyone have any idea what these sliders are called, who makes them, and where I can order some? My one supplier that might have had a lead on some has been ignoring me and not getting back to me on this, I have an order to fill that's long overdue and I'm at my wits end here!