Check these specs out. Looks like a modern AA will way outperform an old
935 carbon zinc C cell hands down. Just wrap your AA alkaline in paper or
cardboard, wrap in electrical tape or spend the money for heat shrink and go
for it.

References:
old C cell (1800mah) http://data.energizer.com/PDFs/935.pdf
New AA cell Page 9 (2850 mah)
http://www.duracell.com/oem/Pdf/others/ATB-full.pdf

Good luck.

PP
.........I wasn't able to force a C in but I did get an AA
in and it works fine. And now I have a manual thanks to Anon at
Bama..............

According to manual at Bama site,
ftp://bama.sbc.edu/downloads/triplett/850/850.pdf

it's an Eveready #935 or Burgess #1 (see pg. 4)..........