SWR SM-400 Fuse Question

[Texan]

This weekend during sound check I discovered that the fuse cap assembly on my SM-400 (one of the originals) is not making good contact between the fuse cap and the rest of the contact assembly for the speaker fuses. I played with it for a minute and got it to work. Is this a common issue with a head this old? I'm planning on ordering new fuse assemblies, does anyone know a good supplier?

Thanks in Advance.