"Dave M" wrote in message
...
Search for Personal Amplifier on Amazon.com. There are several there that
have builtin microphones, but use earphones instead of a builtin speaker.
Prices are generally under $30.

My dad used one of those amplifiers for several years before his death.
Sorry, but it's long gone now, else I'd be glad to send it to you.

If you're into electronics kits, you might check out the kit at
http://www.bgmicro.com/KITMK136.aspx. Looks interesting, small enough to
put into a small box with a battery and carry in your shirt pocket. And
it's STEREO!!

A stereo unit can be a PITA if you only want mono, but if its a common chip
and not already BTL, most have a sample circuit for a BTL amp included in
the appnote.