Many of the truck stops have the cowboy hats. Flying J always seems to have a few hanging around. If you make it to Amarillo, stop in at the Big Texan. The food is great, truck parking in the rear and they have a good selection of cowboy hats, and I believe they may have boots. If you are parked at one of the truck stops, you can call them and they will sent a limo to pick up and bring you back. There are a couple of boot stores near the interstate you can probably park a truck. The Flying J, in Kingman, used to have a guy who sold jewelry. I haven't been there for some time, so I can't guarantee him still being there. There are several places you can stop near I-40 along the way from California to Oklahoma. If you want to drop some serious money on a hat, you can buy a Stetson while you are in Texas.