Following on from my previous advice about looking after your hearing aids I have found the following item on the RNID website to help protect against moisture problems. This dehumidifier has a specially lined plastic that draws moisture out of the hearing aid - it costs only £5.14p and lasts for 6 months!
This is especially recommended for travelling to hot and humid countries and for anyone who goes camping.

Click here for the link
All the best
John