Probably only the original importer could help, unless there's another make and model using the same battery. Batteries similar to this are used on a variety of the cheap bikes that are sold on ebay, but I can't say if any are sufficiently the same. Perhaps a supplier of one of those will co-operate and help by checking the suitability for you.
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Further to my above reply, this battery looks very similar to the one that was used on an earlier eZee model, the Rider. If you use the link below you'll see a picture of it, and you could ask 50cycles whether the batteries are still avaiklable, and their dimensions and connections to see if it's the same.