Making chin supplies

Hello everyone

I am considering making and selling chin toys and cage accessories as I have access to a whole factory and all the tools and wood that I could need. I am based in the UK and was wondering if there are any toys or accessories that people have found hard to get, or have always wished someone would make? Alternatively, what's your/your chins favourite cage item?

Any comments about good/bad items and pics for reference would be great :)