I lost my filler cap back before the Salisbury trip, I left it on the petrol pump. Very disappointed that it didn’t seem to have been handed in as lost.
I had a strip of aluminium and bend it into a rough circle, tried it in the filler neck once, marked it, removed it, drilled the hole and pop riveted the chain fixing the diameter of it. I then tapped it in with a hammer, but it was slightly too small. I was expecting it to be a tight fit, it was lose. Hence the bucked top where I bent it to make it fit tight. That’s now a job for a day when I feel really keen. Likely never.