I believe that the speed, size and power of the .22LR is not enough to make cast bullets worthwhile. Considering that the majority of game taken with the .22 is small game, the upset of the soft bullet is a major advantage over hard cast, who's primary benefit is penetration over expansion.
So, besides needing additional steps in manufacturing, and a potential reduction of performance against small game, nobody is very interested in hard cast slugs for the .22 LR.
Now, when you get up to 35 caliber and larger, with bullets 4 or more times the mass of a .22, and/or speeds in the 1600fps neighborhood then hard cast bullets show a marked advantage over softer ones. (handguns)
With rifles, cast bullets are available in .22 cal (well molds are anyway), and you could cast and load them hard. For .22 centerfires, what you are looking for is harder cast slugs to survive higher speeds. Even with hard cast slugs and gas checks, 2200fps is about the top end you can get with lead bullets before the drawbacks outweigh the benefits. For faster speeds you must go to a jacketed bullet, or be prepared to scrub lead out of your bore every few shots...