By "clasp" you mean a deployant? If so, I know that SMAT/pam2pam makes custom straps for deployant buckles.
If you're thinking of going OEM, unless your wrist is 6.25" or smaller, the regular 115/75 size for OEM straps should work for you. Keep in mind that the design of the deployant buckles makes the straps wear a little smaller than the measurements would indicate (since there is a fair amount of metal between your wrist and the strap).
If you're thinking of going OEM, unless your wrist is 6.25" or smaller, the regular 115/75 size for OEM straps should work for you. Keep in mind that the design of the deployant buckles makes the straps wear a little smaller than the measurements would indicate (since there is a fair amount of metal between your wrist and the strap).