Air filter housing washer

The airfilter housing washer on my Defender 300tdi is tearing and is now holding on by a wing and a prayer. I know that this is not a replacement part but has anyone encountered the same problem? What can I replace it with?

I assume this is the ****ty large skinny ring between the main body of the housing and the end cover. If so, I was going to get a strip of bike tyre inner tube, cut to lenght, glue together and use as a wrap arround to cover this join in the two halves of the housing. Bit like a head band.

Thought this would be far more useful and help keep water out if I get a bit deep Still not done it yet though!

I ran a bead of sillycone round it, let it go off then put the lid on, seems water/air proof to me