Hi Murray,
I don't have a 10-22 any longer, but did in the past. I found that slim filters were best and used a slim CPL and ND with it. (Referring to shooting at the wide end here.) A 3mm thick filter should be fine (possibly a 4mm too, but thicker will likely vignette at the wide end).
I'm not sure if you're trying to use a specific brand of ND filter, but you should be able to find fairly slim ND filters these days. I would suggest Filter Connection (
click here) for a source if your are in the U.S. (sorry, can't remember your locale) though compare to B&H on price. Sometimes they're much cheaper, and other times the same or slightly higher. Terrible site, but nice folks and usually competitive prices, at least on some of the brands. Some items need to be carted to see the best price, even if the site doesn't tell you this. As I said, the site sucks.
I have purchased several filters from them, and needed to return one for a surface defect (not their fault). They cross shipped the replacement and really gave great service.
Good luck...