Every bullet I make can be had with check shank if checks are available for the caliber, and many odd sizes I can and will fit up for larger available checks, which size onto the special shank perfectly when annealed first.
For 41 caliber you'll need 416 gc. Note that all currently manufactured checks sold by Lyman, RCBS and Hornady are made by Hornady and to the same specs. Gater checks by Bullet Swaging supply are good checks, perhaps a bit lower priced in some calibers, and they are the only source for .500 and .512 I believe.