It's a non-standard size. You might as well be looking for a 19/32" wrench.
ANSI, DIN and JIS specify the following bolt and nut hex sizes...
7, 8, 10, 11, 12, 13, 16, 17, 18, 19, 21, 22, 24, 27, 32, 34, 36
Notice how 15mm isn't included but a **** load of metric bolts use it?
Yah, blame...