any suggestions for a low power audio amp for a battery
    operated unit. 1 or 2W, 5 to 6.5V.

Keep in mind your power equation : P = V*V/R

To get even one Watt from a 5V power supply and a typical 8 ohm speaker will
require one of the fancy new complementary-driven amps.  Something like the
national LM4860 looks about like what you're looking for, but this seems to
be a big market segment these days, and there would appear to be a lot of
similar products...

BillW