You can make your own much better. Just be careful when you are skinning the yak not to make any holes or deep cuts in the hide. Be careful scraping the hide too. Then you can either sew it shut while still green and let it dry in the sun to cure or just make a bull boat instead of an inflatable.
Here are the instructions for the bull boat, but you should already know how.
If you can’t find one and have to make it, you’ve identified your retirement job. I do hope you’ll kayak with the yak, though. “Kayak” is a lovely base for a palindrome.
There is a store nearby that sells inflatable sheep. They are, um, anatomically correct and have an electrical plug. I am not sure which emoji most accurately conveys my emotional reaction to this.
Sometimes I think the SDMB is the greatest thing on the Internet, and sometimes I wish I had never stumbled across it. This is definitely one of those times.
On a related note, on the Superman radio show back in the 30s it was revealed that the secret greeting to find out if someone was a member of the Ku Klux Klan was to ask “do you know a Mr. Ayak?” AYAK stands for Are You a Klansman. The proper reply was “I know a Mr. Akai”, where AKAI stands for A Klansman Am I.
Now I want to travel back thru time and be greeted by a Klansman, so I can reply “Is he inflatable?”