Renters. Avemco as a minimum. Just call them, tell them your're a CFI
with 1000 hours tailwheel time, and want to put a Cub or Champ on the
line as a rental, with yourself as the only instructor. No problem. A
friend of mine just made that call. The insurance was available,
though it was expensive.

There are at least two tailwheel airplanes available for rent in
Houston that can be soloed by student pilots.

One is quite expensive, mainly due to insurance. This is because they
will cover minimally qualified tailwheel instructors. 100 hours
tailwheel time, with 15 hours in make and model is the minimum they
will consider, and every instructor must be named. Each instructor
also needs a checkout from the chief instructor, who has literally
thousands of hours in taildraggers. I doubt they would insure a
minimally qualified tailwheel instructor who wants to go it alone.

The other one is much cheaper, but the instructor standards are
significantly more stringent.

Michael