Almost threw out my old Dyson handheld, but then though 'I know Dyson make things difficult and expensive to repair, but I wonder if I can get a battery'. And I could, as easy as that.
Went onto Amazon and a quick search pulled up quite a number of them, different voltage etc. Make sure you check the bottom of the battery you have so that you are ordering the same. Came the next day and it was just a case of pressing a button and pulling the battery out to swap it with the new one.