Nearly all the OHV mowers at my recycle centre seem, for some reason, to have had their air filter covers removed. For instance, I have 4 Ryobi/Subaru mowers and all have this problem. A new one will cost anything from $25 up to $75 (spares.bigwarehouse.com). I can get them from China fairly cheap but it takes a long time and well, these days I would prefer to get them somewhere else. But everywhere else is so expensive. So is there an alternative to somehow make my own?

This is one possibility - Silicone Rubber Moulds. I have been watching YouTube videos of people making silicone rubber moulds and then casting the required parts with resin. There are lots of them on YouTube but here is one: Mould making

The stuff for making the mould is expensive so this would only work if you find a need for a part that you need over and over again or a part to also supply other hobby repairers with them. In my case I find I always need to replace these air filter covers. My plan now is to try and make a "universal" or multi-fit mould and use that for casting so that other brands of mowers are also covered. I know this can be done to some extent since the air filter covers from some other mowers can be modified to fit different ones. By my estimate if I fabricate about 10 of these covers I will be in front.

Has anybody tried doing something like this?