I rarely use standard sizes, either the American inches sizes or International Standards, which the various "A" sizes and siblings are part of.    So,  crop to please and either find a printer who will do any size (specialty, higher end and expensive) or use the larger background with white space.

Yikes, I have paid for an 8 x 10 just to have a decent print of a 7 x 4 or some odd size like that.