Stick Enterprises. Difficult w/ email, but when you call them they are great.
Now, if you don't live in the US you might hafta call in the middle of the night, etc., but bizniz hrs., done, done, and done. Jeff answers the phone these days. It used to be Yuta Chapman or Grace Chapman (!)
Last time I ordered strings, the FIRST TIME since 1985 (!) there was a wrong string & Jeff promptly sent it on it's way. It was a custom gauge set, but the wrong string was not the "custom" part of the set. Also if some sort of hardware breaks (the belthook can break if put under duress) it's off in the mail NC.
VERY small company. Emmett (now Grace) builds them in the garage in Laurel Canyon CA.