.41 Short?
.41 Long?
.41 Swiss?
Any of the above really wont matter. All of them are obsolete cartridges.
Unless you can find an obscure source producing limited runs, you are out of luck. Most collectors that have the ammunition sell it for several dollars per cartridge.
Here is one online example of the prices you'll have to pay unless you find modern source:
http://www.ammo-one.com/RimfireCartridge3.html
This guy claims to have some available.....
http://slickaz.tripod.com/ammo1.htm
If you have a weapon chambered in anything more obscure than these, you'll likely never find the ammunition.