Droid,
We have the Camp Inn side tent that we use on our non-Camp Inn teardrop and we really enjoy it.
I've included the pictures to point out some design features that I feel make it better than a stand-alone shower tent.
It is attached to the teardrop. This has many benefits - a place to store shoes at night, you can change clothes in it without doing the contortions necessary to put clothes on in a teardrop, and it is right there for those late night nature calls.
There are upper and lower straps to snug it to the teardrop. The opening fits around the teadrop door and there is a panel of fabric below the door opening that ties into the floor. There is a flap of fabric that extends over the teardrop sidewall to keep wind and rain from getting between the teardrop and the side tent.
The screened side windows - I believe it is no see-um mesh - allow you to open the teardrop door to get more ventilation and not have to worry about bugs. BTW, there is a strap that holds the door open.
It is big enough to for the porta potty and our clothes that don't fit in the teardrop. The height is tall enough for the average person to stand. If you're tall, you may have to stoop to stand in the tent. The only design change we would make is to make it slightly larger - maybe 1' wider and longer and about 6" taller.
You can tell that a lot of thought went into its design, and their are many design concepts that you could "borrow."
Take care,
Tom