The other related item I was trying to remember is called the Lil Stanker. It is a fan designed for this purpose and uses very little current. Unfortunately, it seems to be unavailable now.
If you're interested, I came across this long thread and will be pursuing some other refinements. The vinyl flap replacement for the Thetford vinyl skirt will be a good start for me.
https://www.trailmanorowners.com/for...ead.php?t=8112
Bill, you said once that you tried cutting the Thetford skirt and it made no difference. I am thinking of trying the same, but cutting it in 1" wide strips. I may just go directly to ShrimpBurrito's solution and ziptie a vinyl flap.