D'Addario EJ22 is 13-56, and its sold as a regular guitar string set. You won't have any issues with that with nearly any guitar bridge. I play them at concert pitch (I tune in parallel fourths with no half step shift, so it's actually Eb/Ab/C#/F#/B/E)
The math works out to 'next string guage is about the same as a half step in tuning or extending the scale length by the next fret.'. So 13's becomes 11's on a baritone at concert pitch. I wouldn't take em any lower than C#, ( but I like a tight long skinny string)