If I've lost this cable, is there anything else I can use to charge up my iPod?

Buy a new one they're cheap

http://www.amazon.com/s?ie=UTF8&rh=n%3A172282%2Ck%3Aipod%20shuffle%20cord&page=1

Most of the iPod shuffle cables shown there are for 2nd gen shuffles. If you have 4th gen shuffle, be sure to buy one that is described as being for the 3rd or 4th gen shuffle. They are different.

Or you can buy the Apple replacement part

http://store.apple.com/us/product/MC003ZM/A