I've been looking online and also asked at Cabela's. No mainstream choices that I can see. I did find this site, that looks promising - the shoulder holster photo includes a Ruger .22 with a scope:
http://www.hidehandler.com/holsters.htm
I also found this suggestion to cut a slot in the spine of a standard Cordura holster:
http://www.thehighroad.org/archive/i.../t-186892.html and some pix
http://www.rimfirecentral.com/forums...=holster+scope
Check the scoped handgun hip holster:
http://www.theconcealmentshop.com/holsters.html
Check Crossman air gun holster:
http://www.rimfirecentral.com/forums...=holster+scope
Also, check out the electric drill holster:
http://www.tools-plus.com/bucket-boss-54006.html and
http://www.tools-plus.com/bucket-boss-54006.html
Let me know if you see anything better!