I'm glad nobody's recommending earmolds. I went that route and found that, after spending the money and experiencing the awkward and time-consuming insertion/removal, they didn't sound as good as the nylon triple flange option.
When I'm on a recording session, I usually monitor with Etys, but I have to be able to remove them quickly if someone wants to talk, so the compressible foam is not usable for me due to that, even if it sounds better in the bass (which it does).
I'm interested in trying some of the options mentioned here - it hadn't occurred to me to look for alternatives like these; I would have thought the shape of the earpiece would allow only the devices supplied by the manufacturer to fit.