Farnell Components in the UK sell Lithium and Lithium Thionyl Chloride
cells from various manufacturers (VARTA, Sonnenschein, Crompton), but
they're all about the same price for that quantity. SAFT also make them.

Also, have a look at:
http://www.varta.com:80/
http://www.duracellnpt.com/explor.d/litsumsh.html
http://www.electronet.com:80/bbase/mfg/m1295.htm
http://members.aol.com:80/solith/Appl-LMNO.html

There are 1.5v to 3v convertor chips, but the quiescent current is likely
to exceed what the PIC actually uses. Maybe there's a cunning method you
could combine with one of these.

I am interested to hear what your solution is - can you eMail or post it to
the list?

>    The only thing I can find that fits is the Eagle-Picher LTC17C lithium @
>$6.64
>each in 100 lots.  Don't mind paying extra for lithium, but that's a bit
>steep!