If indeed you do have a .22-3000 and my faulty memory serves, you can made cases out of .25-35 Win.---not exactly a cartidge you'll find at Wal Mart, but some of the obsolete cartridge mfg. likely offer them. Jump over to the single shot site, those boys will know for sure. I think it was a relatively common wildcat before WWII. I have one round, loaded with a cast bullet, in my meager cartidge collection. It was given to me by a gunsmith back in the late '50's. Good luck with a cool cartridge!
Steve