There seems to be dozens of shower tents on Amazon. It's hard to pick. I have one Cabelas used to sell, and it is good, green, coated with silver inside so you can't see through it. It folds into a circle. The circle is big enough in diameter, it was difficult to jam into my vehicle with the other stuff. My arms are not long enough to pull it open very easily. I would tie one corner to a tree and pull. But it's a good one. I only used it for an outhouse.
I got a second, cheaper one from Amazon, not as big when folded, but I liked the camouflage material. It fit in the Xterra better, but it was small enough, I bumped into the sides all the time, it is shorter in height, and much more difficult to fold up again. I might set it up by the creek and use it for a blind until it falls apart.
The nice two-room type are too big for my needs, although very easy to get up and down. I hate the ones that say in big letters what they are, even if it is obvious.
Lightspeed makes a pretty decent one for ease of operation, but I don't think it is opaque.
I have found one that may be just right. It is bigger across than the Cabelas, but the reviews are so excellent, I have ordered one. It is the single Joolca ensuite which comes from Australia. Joolca.com
Apparently, it won't ship until middle of February. It is dark gray, you can't see through it, slides up and down quickly, doesn't need a rain fly, the guylines stay attached, has pockets for various things, and supposed to be super easy. They also sell a two-room and a hot water shower I know nothing about. I hope this is the last one i purchase. Will review after it appears.
Following up on the Joolca shower tent, single, it is quite nice. After using it a few times (it is really easy to get up and down). I'm not very good at getting the floor folded in to get it back in the bag, however. I really don't need a floor, and consider cutting it off if it won't bother the rest of it. The floor has mesh around the outside for water to run out and keep critters out, but campgrounds are not going to like water and soap running all over. Having a tarp under the whole thing keeps it cleaner. But it is nice, and there are fabric things over where it pushes in, so you don't pinch your hand. It is plenty big, about five foot square at the bottom. I have not had it in the rain yet and have only used it for portable toilet. The shower tent is called ensuite. Like everything, I see the price has gone up since I bought mine.
If it's going to be too windy for my Clam shelter, the ensuite is perhaps a good option.