jdc.i11

Hey, was wondering if anyone could help. I have the above Sharp minidisc player, and when I bought it, it didn't come with the initial power adapter. I've tried using a universal 5V adapter, and it powers up and plays discs, but it won't charge the battery, making the player effectively useless to me. Does anyone know where I could find something compatible, or a way I can get around it? Regards, jdc