Where can I find suitable tubes for Tesla generators and high-voltage experiments?

For Tesla generators, VTTCs and other high-voltage experiments, the tubes sought are often exactly those that have been typical for such setups for years. These mainly include 811A, 572B, 833A or also 810. The 811A in particular is considered a very popular entry-level type in the VTTC scene, because it is widely used and has proven itself in many classic setups; 572B and 833A tubes also appear regularly in such projects. Anyone who wants to replace defective tubes or preserve a historic setup should therefore look for suitable types for the exact generator or experimental setup.