After considering the many options, I opted for a Turbo Toilet from Black Pine. I try not to think about the origin of the name. (But did check carefully to make sure there was no ejection or boost buttons.) It's super easy to set up & fold back again. It is also amazingly sturdy & stable feeling. It is just as low as many other options, maybe 14" tall" but we're OK with that as a camping option. List price is $69 but I got mine off Ebay for $40. For my purposes it is worth the added cost over the bucket & toilet lid combo. If I had more storage space I'd have opted for the luggable loo approach.
http://www.blackpinesports.com/turbo-toilet-blue
[Note: Despite the appearance in the picture, the seat on my toilet is level.]
This is all so my sister has a bathroom in the middle of the night instead of walking to the campground bathrooms. We're leaving on a cross country trip in a week and I DO NOT want to have to get up in the middle of the night to be an escort. Also, I really want her to feel comfortable and enjoy herself. We're in our fifties. When we were kids our parents kept promising us a vacation to California "next Summer" for years on end but it never happened. We're adults now with lots of vacation leave saved up. I finally have a camper & by gawd I am going to make that trip happen now! It might be now or never & never is not an option I'll accept.
Anyway, sis tried the new "litter box" out a couple weekends ago when I set the camper up for her at a nearby park for her dog agility competition. She says it works quite well as long as you don't use the bags that came with it, as those apparently are prone to having holes. Oops. Thankfully she was double bagging as I'd recommended. She switched to using the spare medium sized trash bags I provided. Her verdict is that it's a great addition to the camper for nighttime use. For our trip I decided to add a pop up privacy tent. It's a standy with enough space for indoor potty use but this sharing space with your sister thing has its limits.
Cali or bust!!