As far as I know Crosman no longer makes them. You might find some with a want to buy ad or at an Airgun show. It seems like .20 caliber may be going obsolete as fewer manufacturers offer them. good luck, John
Just looked at the ones I have. They are die lot #4 from the year 2006. Going to need .25 cents per pellet if that's ok. Kidding.
My .20 Air Ranger is a converted 50 ft lb .22. I can only shoot the Korean 24gn ammo. It's insane. I'm running into the same problem you are though. So sad!