This web site has a photos on how to open the Sanyo rice cooker:
http://www.efsowell.us/ed/SanyoECJ-B35SRiceCooker
The solution shown is to install an external battery pack,
but in the battery looks like a 3 volt Panasonic CR-2354/HFN .
(picture is too blurred to read a part number,
so you should check your own cooker).
http://www.digikey.com carries this part
(listed as P274-ND) for $1.90 plus $7.50 UPS ground service
(only carrier authorized to ship lithium batteries)
I used this battery to repair my William Sonoma SR-MK10S
Fuzzy Logic Rice Cooker which is the same as a
NationalSR-MM10N. I found the Panasonic repair manual at
http://www.usersmanualguide.com/panasonic/rice_cooker/srmm10n
-david