You are getting something copied definitely have them remeasure you anyway and tell them to copy style/details of the piece you brought , not the fit. The fabric and the old piece are certainly not the same , so they will hang on your body differently and you will need different measurement. also the owner may consult you on how to improve altering the copy from your original to fit even better ( ex raising the seam of your pants) . Go for it, it’s an opportunity.