I don't know about you guys but all the Local Hobby Shops in my area are T-Maxx, T-Maxx, and more T-Maxx. Shelves and Shelves of t-max. And off to the side, a tiny bit of Ofna, maybe GS stuff. Usually not a comprehensive selection and almost always not what you need.
I bet the hobby is more popular out west, but here in the northeast it's not that big and so really, LHS is likely not going to have what you need. You definately need a reliable online parts dealer for your ride. GS is wicked easy to get from horizon, Ofna parts are available from a few different locations, dunno about the others.
ps. One of the LHS's over here didn't know what GS even was. "General Silicones??" I said, and they said "dunno. never heard of it." Then again, maybe he didn't understand what I was saying because there was so much T-Maxx stuff everywhere you could hardly walk, or breath, or hear anything.