How short, long, compact do you want this motor?
I have a Trix decapod lying around too, and I can find other motors that will fit in there.
But you are going to modify this to make a different 2-10-0, so to really be of any help,
I would need to know how much room (length x width x height) you plan on ending up with
for the motor.
I can tell you this: My instincts are:
1. Any of the convention Atlas/Kato diesel motors are going to be way too large.
2. Mashima (they make a 10x12 x 15mm long and a 10x12x20 long as their smallest)
3. Faulhaber 1016 (10mm round x 16 long) or Maxon 1017 (10mm round x 17 long)
Faulhaber and Maxon also make 8mm diameter, but these are all coreless and by that, I mean
"really good" coreless, so they are expensive (like over $100 expensive).
But the Faulhaber 1016 and Maxon 1017 and 1024 can be had on eBay from microlocomotion (that's Eldon
the "motor man"). You can also email him (motorman@micro-loco-motion.com) That's the quickest way to
ask him what he has. He has a LOT of motors. It takes time because he is an overly busy guy, but
he has the goods for good prices.
He also has the Mashimas.
Any of these options are going to cost you between $35 and $50.
4. Consider the Bachmann 2-8-0 motor. You can buy that from Bachmann's online store
for $12.50... but you may not have the room for it. It is a pretty compact motor and has a decent 5-pole
armature with good power for its size.
But to really know... you need to estimate the room you are really going to have for a motor