You should be able to get hardware for pipes that will allow you to use screws and perhaps washers and nuts to mount an arm around the chainstays if you do not have upper eyelets. I believe you should look for P-clamps because they are shaped like the letter "P" and are made to go around pipes, so check out the pipe hardware sections for a "P-clamp"

Lower eyelets would be better, fortunately, my MTB had them, if not, they do make QR racks that use longer QR and then the arm mounts to the QR.

Jay