Foam / Rubber grip for transmitter wheel

[Ashlandchris]

I have an Absima CR3P as well as my sons Absima CR2S transmitter both of which have a foam grip on the wheel. Both of them have suffered perishing of the foam so I need to replace, but I don't seem to be able to find spares.
Does anyone know what I ought to be googling or where to get the parts?
The foam is 45mm inner diameter if that helps?

Thanks in advance.