I bought mine from these people:
http://www.wirelessmics.fsnet.co.uk/Headsets.htmOne of the very finest 'Le Mans enhancements' I've ever bought. They have gone up a little since I bought mine (actually quite a lot if you allow for the fact that they didn't charge me the VAT!
).
But, if you scroll (about two thirds) down the page to the 'Passive Ear Muffs -FM Pro111' description, the last sentence at the bottom looks like a very tempting invitation. I wonder how many sample sets are available for evaluation in the third week of June?