I emphatically vouch for the Custom Fit service that goes with the Etymotics - http://www.etymotic.com/customfit/index.html - The comfort is staggeringly good and the sound isolation is great. You can happily go running without ever worrying about them getting sweaty and falling out. I've had two sets of HF3s and you just re-use the custom molds. The only criticism I could level at them is that after 2 years of heavy use they tend to pick up a slightly yellow hue from earwax that I just can't seem to shift no matter how hard I try to clean them.

Unfortunately the site's only now to be found on archive.org, but tradepiper.co.uk was all about giving location-specific adverts from both local and national businesses, and this was back in 2001 kinda time. Looks like what the patent talks about matches pretty closely to most of the stuff we were doing back then.

I always compare this sort of attitude to real tangible goods. If a carpenter makes a really good front door, he never gets to charge again 20 years on if suddenly a lot of people walk through it, and if he suggested such a thing it'd be laughed down by any sane person.