Hmm...that's been quite awhile and I'm sure much has changed.
There was one really good store that a buddy of mine had shown me, but I recall he had said he was going to be closing his store and moving to Florida or something - I don't remember the name anymore. I'm sure the store is gone by now.
I did a quick search and one came up that I remembered. Dee's Fabrics & Hobbies, 1316 East Main, Barstow, CA 92311. Phone 619-256-6209. Don't let the Fabrics in the title throw ya. I was a bit skeptical when I was told about it, but they had a pretty good selection of stuff in the back half of the store and also were quite helpful. You might want to call before you head over. I know there were a few in Victorville, but I only went there once for modeling stuff so I really don't remember much. If I needed anything, I could get it in Barstow, on base, from friends or from home.
I know a lot has changed at Ft Irwin since I've been there, but if you get an opportunity to visit the 2/11 HQ - the entrance at the opposite end of the building where the squadron commander's office is - there used to be a display of models (some were put together by an old buddy of mine) which were Sheridan kits modified to look like the VISMOD Sheridans. I don't know if they're still on display, but they were quite impressive models.