I would totally be down for a .22lr 858 conversion kit but I can understand people not caring with $160 crates of surplus.
I wonder how something like this would work though, you'd have to loosen the spring considerably and insert a .22lr magazine into one of the 7.62x39 bananas like they do on the enfield 7.62x39 conversions and put a barrel sleeve into the chamber. It would probably require a whole new bolt. This would not be cheap. How much do other similar conversion kits cost? My friend told me once that he'd probably just buy a 10/22 instead of paying a few hundred to convert one of his guns to .22lr, I totally disagree. I'd love nothing more than blasting 50 rounds out of my 858.