Find a small piece of solid plastic or even a bit of hardwood for the backing, needs to be about 4mm thick, draw a circle on it and sand it down
to the size required (approximately19mm across the middle) ,drawing around a UK 5p will give you the exact line you need to sand it to, I used
the Angle grinder with a sanding flap disc on lowest speed, as long as you have a good eye its perfectly round enough and to size in no time at all,
just make sure you keep your good eye and wear protection!!!
.For the finished top you can use a whole multitude of choices, many breaker cars will have something that's very close to the finish you need, even
some household items will have a surface finished very similar, if you look at the Elan triangle bit that sits over the door mirror screws you will
see a finish that's suitable for the job, so if you had say a broken one of those that would be ideal, but that type of surface finish is extremely
common to find.
Once you have the material all you do it cut a rough circle slightly larger than your backing and then superglue both together, once its bonded
just take the edges down to level with the backing part, maybe go round the very edge with a bit 1k grade wet or dry just to smooth it,
take it to the dash and pop it in place. If your backing part is a different colour give it a bit satin black.
I should really have made a video just to show how easy these are to make, honestly it kids stuff.
Again hard to capture in a picture but they are a pretty good match, and how much to make?
, as long as you cover the backing with something approximating the dash material its all you need.