Propane regulator?

[GTS225-TNT]

Folks, I've been given a vintage Bentley Grillmaster IV gas grill, but the regulator/flame control doesn't adjust the flame lower. I'd really like to make use of it in my outfitting, as I'm going with a steampunk theme for my teardrop.

Might there be a rebuild service, or even replacement parts supplier out there that I haven't been able to find?

Roger