I actually was able to see a couple of them recently at Organ Pipe, Joshua Tree, and Canyonlands. On a slightly related note, there are a handful of other lizards native to the western and southwestern US that aren't held in that many zoos currently, at least according to zootierliste. Some examples include:
- Long-nosed leopard lizard (1 zoo in Switzerland, 1 in the US, and 2 in Russia)
- Sagebrush lizard (0 zoos currently)
- Tiger whiptail (0 zoos currently)
- Western fence lizard (2 zoos in the US and 1 in the UK)
- Zebra-tailed lizard (1 zoo in Spain and 3 in Czechia)