D- Yep that's right price wise.

Oldschool- They actually do make one-




Only problem is that it's a four inch gauge so a bit bigger. I reckon with a bit of trimming you could open up the hole enough to fit the 4" in. The centre hole would look the best to give it a bit of symetry with the single larger dial in the centre.
Autometer do one as well but it's even bigger at 5". That might be a bit of a battle but it would be worth it as it looks nuts!