Found this page YEARS after it was posted, but John Titterington is still working on SRTs, and also occasionally sells them on eBay. In addition to cleaning them and making everything right, he also calibrates the meters to work with modern batteries, which is a far better alternative than the Wein cells most people use.
Originally Posted by bob01721
I had an SRT200 with 45/2 back in the late 1970s, and just bought another one from John. It is OUTSTANDING.