Open up the Ram Mount Catalog and go to "C" Ball mounts that are 1.5" diameter starting on page 48.  These are the most common for mounting ag monitors.  For the rail adapter mounts check out Ram 233 on page 63 or Ram 240 on page 64 these should fit nicely on the round bar in your MX.  If you need bases and the arm look at Ram 101u-CA1 on page 53.

I have ordered a few arms and bases together and then add on specific base mounts for each tractor, combine, etc so they are permanently mounted.  The mounts cost are somewhat expensive, IMO, but it is a whole lot easier moving monitors among tractors with a permanent mount saving time and money.