The closest battery I can find is the slightly larger 2000mAH electrically this is not a problem as the batteries are otherwise the same but may be a little larger than the old battery (Though Slightly longer life). The other option is the smaller 1000mAh
How do you install it?
What is the price please?
Hopefully they Device also has a JST connector though I cannot see from the photo. But all you would have to do is remove the old battery and replace it with the new(Make sure you get the wires the right way round) and you will be good to go!
Prices will be listed on the product page.