It is normally a specialised toothed belt, so you probably need to seek out another Samsung dealer. The side plates may need to come off to replace it (haven't worked on that model) so just make sure you know how the gears are aligned if you take it apart.
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If anyone needs to program a Samsung ER-4940, the manual is here:
http://the-checkout-tech.com/manuals/cashregisters/Samsung_ER-4940_dealer_pocket_programming_guide_manual.html
Registerman, March 2011