Hi!
There is a German equivalent to the DRMO called the VEBEG. They sell all the surplus stuff of the German army, fire depts, civil defense, road mgmt etc. and they have Mogs from time to time. But be aware that the same rules apply as with DRMO: Condition varies and often, it's rather worn out stuff. They also have the more modern, orange colored Mpgs of the road maint - these seem to be in much better shape most of the time.
Check out
http://www.vebeg.de/
If you're not into bidding, don't want to buy a "cat in the sack" (something where you don't really know what you'll get) or don't want to deal with officials who might not be too willing to deal with someone not speaking German in one or the other case, you're better off buying from one of the military vehicle dealers over here. There are a handful of them with good reputation and good quality. Most of them also have a list of for sale vehicles with prices on theiw web site. Check out these two as an example:
http://www.military-vehicles.de/
http://www.padh.de/
There are moree companies like these, some smaller, some more specialized etc. - too many to list. I guess you'll get an ideal on their sites.
Godd luck,
Mike