1. Use the .44, not the 10 mm.
2. A guide with personal bear handgun hunting experience, or a guide with experience guiding handgun hunters for bear? The latter is most important.
3. Alaska: Bruce Parker, Parker's Guide Service, Sitka Alaska.
Lower 48: (Arizona) Sam Ray, Bearpaw Outfitters, Quemado, N.M.
There are lots of others, including some well known ones in Maine, etc. ... if you don't mind being unsuccessful. I prefer success, so you're wise to check references and reputations..