How do I find / buy "pastry bars"?
"Pastry bars metal" seems to work. The results I got were for "caramel ruler bars" or "ganache ruler bars". Other terms are "confectionery rulers" which gave me a forum that recommended getting them cut for you at a metal shop from stainless steel at whatever lengths you want for less than buying purpose made ones.

That said, I'm not sure that's actually what you're looking for. These seem to be bars for rolling out dough or fondant to a specific thickness, not designed to be used for shaping things the way your photo implies.

The term that I found that more closely resembles what you're looking for is "confectionery frames".