Helpful thread and just got a travel letter from my NHS sleep service - assume electronic copy is ok?

One question I had from those users in this thread. Have you been able to find a battery that airlines will allow you to use?

I bought one from Amazon. When it came it was huge and had a large badge on the front saying “not airline approved” so had to send it back.

Would still like to buy one as per BAs advice but also got some sleeper train journeys due for which it would be most helpful.