It is very hard to find.
C-tech collective have an english user / programming manual here:
http://the-checkout-tech.com/manuals/cashregisters/Sharp_ER-A490_instruction_english_manual.html
Also, the dealer manual is here:
http://the-checkout-tech.com/manuals/cashregisters/Sharp_ER-A490_programming_manual.html
If you are setting up the machine from scratch, get the dealer manual as well. Just copy and paste the links above into your browser
Registerman, September 2010