Remap mouse button 8 ("browser forward") to mouse button 2 ("middle click") on RHEL

What would be the proper way to remap mouse buttons on RHEL? xbindkeys doesn't seem to be available on my repos (not RHEL default, but enterprise custom repos). I guess I could install it on my own, but even then, I don't know how to create a proper xbindkeyssrc file.