The top floor room (westernmost room) in which the Steamwork Trainer spawns is marked on the Meldrath's Mansion maps linked from the top of the zone page.
Steamwork Trainer also dropped an evolving item called a Gnomish Fabric-Mauling Button-Holer. I have a screenshot and I'll try and figure out how to upload to Lucy.
Forgot to get a picture. Dropped a Steam Core: Purification and Tiny Clockwork Shaft. No special procs or AE's. No rampage but did enrage. Both times we pulled him, a game piece came with him, but I can't tell if they're attached or if it spawned after the pull. Was able to mez and memblur the "a game piece". The max hit on the tank was 2079 (tank is over 4k ac buffed), but the cleric (that would be me) got hit a good smack for 3672.