I didn't know there was a proper sram one. If there is, cool as I may look for one myself. I had a similar need a while back and a member on herw supplied me some that were custom made for the job from some aluminium tube. I recently gave someone some cut off seat post from a 31.6 tube that they used as a front mech shim though that might not work for the size you need. If the shimano ones fit, I'd be tempted to use it unless there is a proper sram one.