I have a requirement to make some form of damper for a Swing Arm on a piece of equipment we manufacture.  A mountain bike air shock absorber would probably be ideal but decent examples retail for around £200 which is a bit expensive.  A "bump stop" type of device would be adequate (depending on material) and I have searched for suitable materials that we could cast in house.  Sorbothane looks like it would be suitable but it looks like I can't buy this as a resin and there is poor availability in the UK (unless you want insoles for your shoes!).

Can anyone recommend a suitable castable resin?

The Swing Arm is around 500mm long with a 6 kg mass on the end.

Ewan