For the Mini Guitar Kits, you can use a standard guitar string set starting at .009" or .010" gauge if you tune A to A, similar to having a capo at the 5th fret of a standard-scale guitar.

If you want to tune a full octave up to get back to E to E tuning, you can use a .009" set but will need to replace the high-E string with a .007" gauge string. Otherwise, it may break from the added tension. You could also use a set starting with .007", such as our item #1346 Dunlop Reverend Willy's Electric Guitar Strings.