I got mine from Groovy Game Gear, when I bought the moulding. Interesting enough, I flipped it over last night, and now it works perfectly! No more acrid smoke!
Ha ha! I did that once myself!
T-molding barbs vary, not only from manufacture to manufacture, but also depending on the head and speed of the extrusion equipment. Most of the time a 1/16 inch slot bit works fine. BUR, unless the price is outrageousness, I'd buy it from the manufacture--then you know you're getting the right bit.
Also, it sounds like this is the first time you are cutting a slot. I'd recommend cutting some scrap wood (especially on the curves). It takes a little practice to not lift the router up slightly when you go around curves.