Trainworld.com could be a good source for factory made donor mechanisms; just browse the N scale Bachmann section
http://www.trainworld.com/
George In Midcoast Maine, 'bout halfway up the Rockland branch
OK now that I'm back on desktop and can partially actually go to the referenced site. I agree with Ulrich, thats a custom scratchbuilt job, there are similar 3 axle drives in N scale, Bachmanns industrial switcher comes immediately to mind, however it has no siderods,
http://www.ho-scaletrains.net/bachmann-nscale-locomotives/id192.html
Atlas/Roco makes (or made) one in European dress that might work as a substitute:
http://www.spookshow.net/davenport.html
Have fun with your trains
Looks like a scratchbuilt chassis to me.
vsmithNot knowing what it
back to the original question
Not Knowing what brand of kit, or brand of donor chassis it was you saw, its very hard to offer any advice on drivetrains. Can you provide actual information on what you saw. Brand? Kit?
Most HOn30 donors tend to be easily available N scale model brands like Bachmann or Atlas, Bachmann makes a good 0-6-0 chassis in N. Atlas also makes an "Old timer" 2-6-0 that could also be a donor though a bit pricey.