Hytrel is a common plastic material that is very durable. It is typically used in sports industry for things like snowboard bindings and ski boots, and also in automotive industry. The 30D is very flexible like rubber while 82D is very stiff. You can get a Hytrel swatchbook in different hardnesses to get a feel for what you want. However, the geometry will still have great effect on the result. Meaning you could get the desired results by selecting a harder material but changing geometry of the bait. I actually designed a product a few years ago with similar trade offs, and we ended up selecting Hytrel for our needs. Some areas had to be strong, others soft etc. Let me know if Tim can’t solve your problems, perhaps I could help you in exchange for $.
http://www.toolgurus.co.uk/9716-hammer-holder/