Welcome to the forum, Dean. You are correct in noticing that 13' Casitas are relatively uncommon. Casita
sells a lot more larger units. I have seen several 13'ers on the market this season, though, so they are out there. If that's what you're set on, you will have to be patient and keep a close eye on all the different classified sites.
sells more 13'ers and they're far more common on the used market. They are also available with a front bath. If you get a newer one (2007+) it has several inches more headroom inside that the Casita. It's a bit better insulated, too. But I guess I'm biased...
Be aware that with Casita, "deluxe" means bath models, but with Scamp
, "deluxe" means wood interior versions.
Good luck in your egg hunt!