Discovered this begonia in a glasshouse, not for sale. I was interest to know the name Couldn't find one with yellow flowers and green crinkly leaves

Maybe Begonia microsperma.

Quote....... below from......
https://plantophiles.com/plant...

"Begonia Microsperma is a rare Begonia species that is native to the tropical regions of West Africa, specifically Cameroon.

This plant develops small, eye-catching yellow flowers. This rhizomatous plant has textured leaves with tiny hairs."

https://www.google.com/search?...

thank you
I believe that is it