I've never seen one in the states. Even this species probably lives in localized higher humidity areas of the desert much like the veiled does. They actually live in densely vegetated coastal river valleys that get a lot of fog and dew. You can get around the low humidity problems in several ways, so keeping chams in the "desert" can be done. I've kept high humidity species at higher elevations in the Rockies and THAT is DRY. Actually, most of us in the US keep ours indoors, and indoor climates are almost always too dry for chams (think AC in summer, furnace heat in winter). The only cham that can probably take the 20% humidity level is the Namaqua and again, you just don't see them in the hobby.
Temperature in summer may be the bigger problem if you live in a hot climate. If your home stays over 80 F in summer you will have problems providing the 15 degree temp drop at night that chams require without using AC. If the outdoor temp gets up to 100 F much of the summer that may be too hot to keep chams outside. Remember too, a cham's entire cage shouldn't be kept at the same temp. There needs to be a gradient of temp and humidity so the cham can self regulate. A basking spot provides a warm area but the rest of the cage can be cooler and moister.
So, you'll need to create a higher humidity microclimate in your house indoor cage by using lots of live foliage that will absorb and slowly release moisture and lots of daily spraying or using foggers or humidifiers. Even the veiled often sold as a "dry climate" species needs at least 40-50% relative humidity. A veiled or panther can take warmer temperatures, but you will need to provide a temp drop at night and a lot of water during the day. There are some good keeping articles on the sites listed at the top of this forum, so do some reading there and come back with specific questions, OK?