Copying everything from your SD card to your PC and then formatting the SD card with FAT32 Format and only copying the n64.txt to the root of the SD would be worth a try.
Any 5V/1A USB 2.0 phone charger from a reputable manufacturer should work. Just stay away from the $2 Chinese clones.
I just tried an original Apple Charger from an Iphone 4 or 5 and that worked flawlessly too, even for unlocking SA-1 SNES carts.