Batteries plus can get those batteries.
If I remember correctly there is a conversion kit for it too that will change it over to 12 volt but you will need to swap all the light bulbs out for 12 volt ones. If you plan to ride it alot I would look into that.
When the system fails you, what then?? Do you fight it or just surrender and give up? If all seems doomed what is left to fight for? Is it just me or does the world seem to close in on you when you seem to be making ground? Options are dwindling down, what comes next? And in the words of Pink Floyd "Is there anybody out there". All I know is I WILL SURVIVE.