Ammoseek shows quite a bit available - but it's very expensive.
No matter where you buy it today, .22 WMR is going to be sky high expensive. (9 MM Ball will be substantially cheaper by comparison). I just think it's demand, nothing more. .17 HMR seems to be in good supply, at least around these parts. That's because the .17 HMR has only been around a short amount of time compared to the .22 WMR, which was introduced in 1959. So there are tons more .22 WMR rifles around.