Hardware help, does this exist?

Hi, please forgive my naive question. I'm looking for a corner-to-corner hardware connector for wood, as in this sketch. If these commonly exist, I can't figure out what they're called?

If not, I wonder if they would be straightforward to hire someone to make?

The situation is I have a salvaged "apron" tabletop without legs, and I'd love to set new legs further out than in the original design. Otherwise my chairs won't fit between them on the narrow end.

Apologies for being rather off topic & thanks! 🙂