I've got a wooden knob that my father turned on his lathe
many years ago which fitted on something I was driving back then.
I modified it later to have an 8mm side grub screw, also bored out the centre
to, I think, around 10mm.
I like the personal custom concept , so if you have a friend with a lathe or a local engineering shop
you could have a wood/aluminium/plastic thingy made up to suit.
Alu is a bit touch-cold though, depending on your climate!
Options are endless fun.
Nigel