I have done a search, both on line and on ST, but cannot seem to find any wisdom on how to install a chain catcher on the SRAM Red non-braze-on front derailleur. The clamp band does not have forward facing bolt like a braze-on or Shimano derailleur - anyone else have this issue?
If you are looking to use the K-edge chain catcher they do a version with 31.8 and 34.9 seat post clamps.
Alternatively look around for an aftermarket frame clamp that would be used to mount a braze on front mech to a frame without the bracket. Although with this second option you would probably need to mess about and fabricate some spacers and things.