I know King Amplification does them and they do a great job, http://www.kingamplification.com/
I was going to do the same on an amp and did inquire, at the end I just went with an attenuator. The attenuator was more affordable and I didnt have to alter my amp circuit at all.
Jack, the Aracom PRX150 you have on order will obviate the need for power scaling. I'd leave the amp stock and just add the attenuator. It takes a lot of fiddling around to make PS sound great on any given amp. It's highly dependent on the expertise of the installer.
Ironically, I just ran some tests this morning comparing power scaling on my Badger to running it full power and using the Aracom to attenuate. John's implementation of power scaling is absolutely amazing and there weren't major differences between them, but I did slightly prefer running the amp full power and using the Aracom to knock down level. Seems like that approach gave me more clarity and sustain but without too much compression. PS seemed a little more compressed at the same overall distortion levels, probably due to the lower voltages. You also drive the OT harder with the attenuator which can also add compression in some amps, but not with the Badger, at least not at the Drive settings I used.
If the amp already had PS, I'd use that or try the Aracom and see what you like best, but since the amp does not have PS, I wouldn't alter it. Might reduce resale value. The Aracom will give you exactly what you want out of this amp w/o altering it.
how does skips circuit compare to the london power circuit? It looks to be 1/10th the components...I'm getting an aracom eventually but not sure when that'll be. I doubt installing PS in a metro will alter its value. I only paid $750 for it in the first place. The big advantage of the PS is that it's not wearing out the tubes and transformers.