Hi. I recently got an old European road bike, and I need to adjust the handlebars, but I can't find a hex wrench that fits the socket. 6mm is too small, but 8mm is too large. 5/16" is too small, but 3/8" is too large. (At least, I think it was 3/8"; it mighta been mislabelled.) And my local hardware store sells nothing in between those sizes that I've mentioned.

Is there some funky hex size that's standard for bikes which I wouldn't find a small, poorly-organized hardware store? Or does anybody know where I could order a 7mm hex wrench for cheap?

Thanks.