Sometimes it isn't possible to find spare or re-manufactured rubber parts but, provided it isn't a precision part, it may be possible to make your own from a product called 'Flexane'.
Available in several hardnesses, we chose Flexane 94 (one of the hardest) to remanufacture the suspension bushes for the 'dog bones' (8 of - shown fitted to parts 131021, 131022, 131312, 131313 but without individual part numbers) and the rubber stops which sit in the front suspension hangers (2 of - part 412872 including bonding to metal plate). In retrospect, Flexane 80 would probably have been a better choice (the suspension is now remarkably 'firm'!) and Flexane 60 (the softest) would be a good choice for grommets, boots etc.
Unfortunately, Flexane is neither cheap nor easy to work with and the first batch may be best considered a learning exercise. The following points are important to remember:
1) The exterior finish quality is entirely dependent on the quality of the mold. Spending time polishing, lubricating and otherwise perfecting the mold will pay dividends.
2) The mixture comes in two parts - unfortunately both are the same color which makes ensuring even mixing quite difficult. It is imperative that the two are well mixed however and in exactly the proportions instructed, or some parts may not cure correctly (or at all)
3) Heed carefully the instructions regarding working temperature and setting time - the shelf-life is not considerable once opened, so it makes sense to mix and use the entire contents of the tin at once. Prepare sufficient molds to make best use of the rubber.
It's worth mentioning that a metal-to-rubber primer exists (ideal for part 412872), but note that the rubber can't be bonded to metal after it has cured, so after priming, the metal should be used as part of the mold.
Plaster of Paris is recommended for the best molds, using talcum powder (mottled finish) or vaseline (swirly finish) for the releasing agent.
An important property of Flexane is that parts made are resistant to petrol, oil and thinners.