I was lucky to come across today a chassis of a TK23 that was being dumped away after the machine was being stripped off its goods inside (only due to a number of cracks in the top panel and so on). I managed to strip off the mesh using a hair dryer and a scraper and I think I will be able to fit it onto the TK20, with some modifications perhaps. It cleaned up very nicely and it looks whiter than the covering on the TK20. It will definitely be an improvement then as it looks at the moment.
I shall post photos when I get the job done, fingers crossed