I'm not sure if this will help but over the last 20 years I have gone to TOCOS (Tokyo Cosmos) potentiometers.
They come in 24 or 31mm diameter (and there are smaller 16mm ones too), with & without switches and dual gang. I got totally hooked on them after buying them in Akihabara in Tokyo and being impressed with the quality. I've used them in practically every radio home brew project, amplifier repairs and restoration project. Their quality and construction is outstanding/unmatched. The only disadvantage is they are Metric, 6mm shaft and 9mm mounting hole. The range is 50R to 2Meg. I have worked around the metric issue with thin shims and use a type of slim line shaft extender where required. They have a sealed construction.
I noticed recently that the manufacturers have an English website so it looks like it is possible to buy them now directly from the factory. Many Japanese companies now have overseas sales department and accept paypal.
The type I'm talking about is near the bottom of the page on this link:
http://www.tocos-j.co.jp/e/catalog/pot/pot01.html
After using these it is just about impossible to go back to most other products.
If you scroll to page 10 of this article you will see an array of the 16mm diameter versions I recently used to modify a video monitor:
http://worldphaco.com/uploads/Autode...e_monitor..pdf