How to make a custom USB cable for a Finis Neptune MP3 player?

[niceties55]

Someone gave me a swimming, underwater Finis Neptune MP3 player but the problem is the charging cable was not included. Since this is a waterproof MP3 player the cable is proprietary and it is impossible to find a cable (from the company or otherwise) without buying a second unit on eBay with the cable.

My 1st question: Is there a way to cut apart an old USB cable and make my own charger/transfer cable?
My 2nd question: There are four contacts on the bottom of the MP3 player. How do I map each one to know what is positive, negative, ground and data transfer? (Photo of pins attached)


Thanks!

 

[AMD_man]

You would need schematics of the circuits used to charge the battery. Also knowledge of how USB cables transfer energy. Why are you so sure you'd need to modify a USB cable and not something else?