I borrowed a Nano as a backup for Uvalde Glide and was impressed with
its simple operation. The Colibri II seems to also be a good option,
though neither are "cheap". The Colibri is currently on sale as they
clear stock. Any of these should be nearly a direct replacement for
the LX20. Inexpensive alternatives are as mentioned above - most of
the current PDA software will generate files acceptable for IGC (GNII
is an exception) and all you need is the GPS source, which you already
have with the LX20.

Cheers,

Derek