Amazon Search for Hibiscus Denudata gets one hit for a few seeds.

Here is a link that might be useful: Amazon

That plant is on the Desert Survivors nursery (in Tucson) plant list. Which means they may (or not) have it at their spring plant sale in March.
I picked up a Hibiscus martianus (H. cardiophyllus) there during their fall plant sale. They had several different varieties of native Hibiscus.

Thanks for the info. I will surely try this Tucson nursery.