I have been given three US firms that do dual gauge rebuilds. I have spoken with with APT and they said $165 and a turn around time of a month. I have heard good and bad about all three at one time or the other. It seems that the west coast people prefer MoMa's and the east coast people prefer Nisonger.
Here are the contacts.
APT Instruments International Inc
9632 Humboldt Ave S
Bloomington MN 55431
952-881-7095
Motor Mart
10853 Magnolia Blvd
North Hollywood, Ca
(818) 980-8642
Nisonger Instrument Sales and Service
570 Mamaroneck Avenue
Mamaroneck, New York 10543
(914) 381 1952