Ryk,
I've been using Sennheiser IE4s on the lawn tractor and they work pretty well for a unit that just uses a generic rubber fitment and the fidelity is very good. It really depends on how good you can seal that ear canal and these work for me in that environment. Gotta crank them up using the wood chipper and that might be uncomfortable for anyone with acute hearing...

A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)