At first I thought that specific name -- anal hole spreader -- was more of a slang or casual term, until I googled it. I believe it does have some advantages over the 3-armed version recommended above, but if quality/smoothness is an issue, definitely be cautious!
I have seen both types used in actual medical/surgical videos I've seen. And, in fact, on a surgical instrument site I recently stumbled across you can see a variety of styles including both of the aforementioned ones:
I also came across this one, which definitely appears to be non-medical in purpose, but looks like it avoids the pinching issue and still doesn't block the view much. It's called The Hole, also referred to as a ring speculum and this is the only place I've ever seen it:
FTR - I don't have experience with any of these, I've just read and browsed quite a bit over the years so take my comments with a grain or two of salt