Moulding with Clear Resin

[Jim H]

Hi,
I'm carrying this over from the Classic Car section:

I'm wanting to recreate the clear lens/bubble from the top of the gear knob off my classic, it's a rare item and difficult to replace.
The lens has a crack in it which spoils it, I've managed to remove it in one piece and the advice from others - this should me fairly easy to recreate in clear resin from a mould.

Any tips on material & suppliers, tutorials, videos and advice would be very welcome..

Thanks in advance Jim.