The four words that most strike fear in a husband's heart: "I have an idea ..."
However, in this case I think She (Who Must Be Obeyed - aka SWMBO) actually has a pretty good one.
She looked at the outdoor shower, tucked neatly between two slideouts and said: "All it needs is a floor and a shower curtain".
Something like this for a floor:
http://www.walmart.com/ip/Pollenex-T...er-Mat/4328466
And a tension rod between the slideouts to hold a curtain.
Now, I wouldn't use it without wearing my bathing suit, so I'm not sure why we need a curtain, but I do like the idea of the "floor". And if a curtain makes Her happy, then I'm happy.
SWMBO wanted me to post to see if anyone else has done something like this.