If the T power supply is like the other large Sunn amps, copied from Dynaco, then all the current powering the amp passes thru those chokes. The Dynaco part # is C354, and several outfits offer them: Triode has their 3-10C, 1.5 Henry, 200 mA, and boasts a 2500V hipot test so presumably there won't be any problem with leakage to the laminations & frame. There may be other sources. It would be nice to have a larger current capacity as 200 mA is barely enough to provide bias current for the output tubes plus current to run the pre tubes.
Some data on C354+ which features a 300 mA spec. http://www.classicvalve.ca/docs/C354+_docs.pdf
diytube had a discussion a few years back which may guide you to an alternate choice. Looks like the Hammond 194G may be a candidate, if you have enough room in, or on, the chassis.
diytube.com ? View topic - Choke replacements