Sig has not released them yet, as far as I know and I try to stay on top of that because I am a P250 owner.
Look for them in the next 6-8 weeks. Which translates into 6-8 more months.
I think Buds had CPO's for $399. That's about the cost of the kit when they come out. My suggestion to them is to make a .22LR kit for it. I think that would be the most popular.