Another vote for the moulded plugs from A1 Hearing. Had a pair made up in 2012 and have been very happy indeed with them for use in fullbore TR and they're still going strong. I'll probably get a replacement pair made at some point this year as they get a lot of use and the surface is starting to break down in one or two places.
I do use proper ear defenders when coaching or plotting though, as I've also heard that sound can cause damage through the surfaces around your ears.
Gaz
NB - Disclaimer! The lady who runs A1 Hearing (Carol) is a friend of mine.