Never really widespread, but there were some around at one time, maybe half a dozen or more US zoos? San Diego had them, even a small camel farm in Yuma, Arizona was listed as having them years ago.
@devilfish I saw a recent photo here of a pair at Henry Doorly Zoo. But I am surprised you say there are also some at the Safari Park, since that is strictly North American wildlife. Do they have them in an off exhibit breeding center there?
BTW The Living Desert (pictured here) no longer has any. They also no longer have these exhibits (which honestly were too small) and have moved their other small cats off exhibit (ie sand cats and black footed cats). I have heard of no plans to put them back on exhibit.