Steve,
I bought a replacement Ocean Line VDO Voltmeter from Egages (part of Don's
Sport Vehicle Sales) last year.  Take a look at:

http://www.egauges.com/vdo_grou.asp?Series=OL_BL_BL

They show a limited stock on Blue Line gages since they are discontinued but
have the full set of Ocean Line gages.

Another source is but I haven't purchased anything from them:

http://www.vehiclecontrols.com/products/vdo.htm

Bob Williamson

Lewis Marine also carries the Ocean, and I believe the Blue line VDO guages. They can be found by googling Lewis Marine.

Rudy and Jill
Briney Bug, Panama City, Fl