Couldn't find good priced one on Ebay, would most likely go with Amazon. Hard cases (unless more expensive and made better) tend to get dust under them and scratch the phones outer shell (have had it happen). Unless the MT is just awesome and scratch resistant...I wouldn't go with hard shell case until someone like Otter Box makes it. I usually go with a jelly case.
Amazon.com: Amzer AMZ91931 Silicone Skin Jelly Case for Motorola TRIUMPH - 1 Pack - Frustration-Free Packaging - Black: Cell Phones & Accessories
Something like that would do. You want to make sure with any case that it has an opening for the back noise canceling spot by battery, and enough room for camera there. That case looks nice from the picture, and is probably what I am about to grab. I've always had those jelly cases, great for me because I drop my phone a lot. I like to play with it, flip it around etc...
With jelly cases however, they get stuck going in and out of most pockets in pants. This can be a problem for some, so another to look at would be this one:
http://www.amazon.com/Amzer-AMZ91949-Argyle-Motorola-TRIUMPH/dp/B005ER3RZO
More stylish, slightly transparent, and smoother to the touch so not as hard to get into and out of pockets. I won't get THIS one because it has no headphone jack cut out. Also, I think it may still be too hard even though it's almost as flexible as pure jelly case. I'm still afraid of the dust thing happening again. I want a slightly harder case, but not a <$12 case. I want a nice otterbox case but they don't make it yet. Jelly case will add more bulk to phone than some hard cases.
LAST, but NEVER least. I suggest this hands down:
Motorola Triumph Screen Protector & Phone Cover | invisibleSHIELD by ZAGG
It's virtually invisible, and won't hardly snag on your pocket. I would get the full body or if your confident...maximum protection one. THEN I would put on a fairly nice hard case over that. That way, the zagg protects you from scratches from dirt and such under the case, and the case helps with farther falls if you get one like that TPU gel case that is semi hard. Zagg screen protectors are the best. Now your triumph already has a built on one with the Gorilla Glass... so either you will want to peel that off and put on the zagg. Or in my case i'm just waiting for mine to get scratched and then will put on a zagg. So far factory screen protector is holding up just fine.
So my suggestion, Zagg, and semi hard case over.