diy something then. You know what materials work & what you have. The only thing I don't recall mentioned was epoxy & fibre, either glass or paper.
Last one I fixed had all its cores firmly seized. Turned out its sensitivity problem lay elsewhere & it didn't need a tweak. Did not want to rebuild the cans. Had already worked out a sneakaround but not needed.
The problem with seized cores is that the inductors they tune are typically in parallel with a fixed capacitance. So even though the cores have never gone out of adjustment (cos they're seized) the value of the capacitances they resonate with will have done - and those caps are not adjustable. So in order to re-align that stage, you have to somehow free those cores. There's no practical alternative and if you have to destroy and replace them in the process, then so be it.
The practical alternative I came up with was gimmick caps. But not needed. Realignment may be popular, but is not always needed, as in this case.
That's a bit "old school", Brian. For £60 and upwards you can get a Chinese nanoVNA which will do all of that and much more besides.
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