%The Lost City of Overton Museum has a small gift store that offers replicas of the Petroglyphs as well as local/American Indian hand-crafts and jewlery. Some of the stuff is the typical tourist items, but also some interesting replicas.
They actually have an On-Line Store. Take a look at their inventory to see what might interest you.
When I was here there was a small general store. Actually it was more of a pre-fab trailer and looked more like a warehouse than a store. It was operated by the Moap band of Paiutes, who were very nice and friendly.
Well, since that time they have added a few other things, gas, food even a casino. So this is now a real convenience stop.
What to buy: I'd fill up the tank because this is the only gas station for many miles around. I'd buy something to snack on in the car or items for a picnic out amonst the rock formations. I might gamble a little but I wouldn't buy any firecrackers!
Of course, you could buy what ever you want or need.