I know Kurt Williams with Cruiser Outfitters is capable of getting Montero Part from ARB. He is located out of Salt Lake and he is the best. Everyone loves Kurt because he runs a great business. Personally I would go with Kurt. He sells a lot of ARB parts. I know his site list just Toyota parts, but he can get his hands on anything ARB, OME etc. He just lists the Toyota parts because those are the ones he has in stock. It should only take him a few days to get the Montero parts.
http://cruiseroutfitters.com/
1985 Mitsubishi Pickup, 2.3 H.O. Turbo Diesel, Watercooled Turbo, ported and polished 4D56 Head with Roller Rockers, Custom '83 Injection pump, JK Rubicon axles w/elockers and disc brakes, 14" Fox Coilovers, Centerforce II, 5.0 Atlas II, ARB Bull Bar, 33x12.50x17 General Grabber Competition tires
2003 G-Class
2005 GMC Sierra 2500HD 4x4, Duramax, Crew Cab, 6 speed manual
2009 Jetta Sportwagen TDI, 6 speed manual, NAV, PANO, most underated expo vehicle ever........