Any good pilots shops you can actually walk into and buy things

at the risk of self-promoting, these guys are pretty good - www.pilotshop.nl

For the Lemo-plug Bose X, such an adaptor is not possible unless it has an internal battery. I built one a long time ago but have never seen one for sale. Normally, to convert a Bose X, you replace the whole mike cable - about £150.

For the Lemo-plug Bose A20, which for some bizzare reason does have an internal battery, such an adaptor does exist for about $50. I've never seen it for sale in Europe. I had one on order from the USA but it never arrived.