Hey Crusher,
I picked up my pump from rc4wd.com but you can also get them here:
http://www.magomhrc.com/en/13-hydraulic-parts
Haven't had the opportunity to actually run the system in full but it is the same pump that comes in the 4200xl excavator they sell.
Although I may end up trying to magom unit with an integrated tank.
Hope this can help ya out,
Chris