Ultracote is made by Hangar 9. I think it originally was a Goldberg product, but I may be wrong.
All the rc (never capitalize) wholesalers carry it. Tower Hobbies, Hobby Lobby, Hobbico, etc. Do a Google search.
It comes in two weights. I use Ultracote Lite for 1/2A’s. Regular UltraCote is used on anything gas above 450 square inches. You will find it is really easy to use, and is a bit stiffer than Monocote and Coverite/Coverlite.
Easiest iron-on I have ever used.