ktm macina battery replacement

#1 I have a volt alpine which I consider my mobility scooter I have owned it since 2013 a new battery cost 340 pound so I bought a mid mount from China which I am hoping to run on my cheap Chinese battery but I have looked at the bottom of my volt battery and I can't see a + or - just four pins...

Can anyone advise where best to obtain a spare Bosch power pack for this bike? I think there may be a couple on Amazon and maybe I have found one on Ebay, but I'd far prefer to use a source that guaranteed compatibility. I think my existing pack has 300 Wh and I'd love to upgrade to 486 Wh...