I think this is exactly what you are looking for. I found them at Dallasmodelworks: the Nordburg Hydra Hammer, also the Hammer Tamper Track Alignment with buggy.
I searched under Rolling Stock and by Road (Alphabetized), they were on the last page under "unlettered". If I knew how to use the computer better, i could have done the link thing.
There is also one made here in Minnesota, comes as a kit you assemble, but I couldn't remember the name. I have a paper catalog at home, and I can look it it up and report back tomorrow.
logandsawman