Etsy, eBay, Steve's Leaves, Taylor Greenhouses, Logee's would all be good places to start your quest for a beefsteak begonia. Local nurseries sometimes get some old time begonias in as well.

Doing a web search might drum up some smaller sellers as well. Seems like FB has a group that buys/sells begonias.

Hello,

Yes thank you for a answer to my question. I have done searches online and nurseries close by. I didn't have a very good time buying on Etsy.

I'll do more searching.

Thank you

I'd try Steve's Leaves and Taylor Greenhouses, then.