I got this idea from a White Dwarf photo of a Tallarn gunner on a Baneblade. It's a gunner from a heavy bolter or autocannon. The down side is that without bitz ordering, I had to buy the entire $15 blister to get this one guy. Now I understand the annoyance from veteran players about the program change. The machine gun doesn't quite fit correctly with the gunner, but it works when I remove the mount.
The other option was a Forge World Tallarn Gunner, but with my discount, the standard gunner is cheaper.