I'd think less in terms of 'wax', and more in terms of abrasive. The bar-type compounds do use some wax-like binders to hold the abrasive, but it's the abrasive that gets the job done.
At any rate, most any hardware outlet that carries bench buffers/grinders will also carry compounds made for them (this is what the bar compounds are made for). Sears, Home Depot/Lowe's, Ace/Tru-Value might all be good places to look. Woodworking outlets, such as Woodcraft (where I got my green compound), also carry them. Compounds can usually be found in black (silicon carbide), white (usually, but not always aluminum oxide) and green (chromium oxide).
I've no idea how 'Turtle Wax' might work. If it's the rubbing/buffing compound (probably containing silica abrasive), and not just wax, it might work OK. Wax by itself won't do anything (no abrasive). I've heard and read here that Mother's Mag Aluminum Wheel Polish works, but I've never tried it myself.