In Ctown as you call it I've bought at both Wholesale & Pro-line. I think there is a gunshow coming up at Thorncliffe and I see then on tables now and again.
I have built my own "cutter (as others have mentioned) for the Aluminum GCs but there is more to it than they mention, at least in my trials. If your mold has the GC base for factory checks then the alum will be too thin. You will need a very robust cutter/ press to make checks from heavy enough metal that they will perform and grip the bullet base.
I have had good luck with the home made GCs gripping and staying mounted to the base of a very flat based bullet but any bullet with a bevel/rounded base has trouble holding the check in place.
I think homemade have their place, fun to experiment with and almost costless (my punch is homemade as well, plans on the CAST Boolits site) but do they replace the store-bought in all uses...I think not.