[Invalid or Expired Link Removed] has both as well as the non extended length Pyramids. So if you really want the LaBellas, you can get them there. That said ...
I hate LaBella strings. Always have - both in feel and sound. I'm a Roto guy. The RS88 was the mainstay of my fretless basses for a long time starting with the G&L L2000 I got in the early 90s. I experimented with the 760N set in the late 90s and they were on for less than a week. The RS88 was on both of my D4s. The Galli was the first non-RS88 in a long time. I felt the same about the Jamerson set (the 1954 ones). I love thick, heavy, mucho tension flats. The RS77LE set is my mainstay on the P. The 1954 set was the worst set of strings I ever played. The feel was terrible. Others will, I'm sure, say different.
The RS88 and 760 sets are both high tension, so feel wise they'll be more similar than different. I remember the 760 also being a bit stiff (again, similar to the RS88).
Sonically I don't remember what the 760N set sounded like, but I didn't like anything about them. They couldn't be gone fast enough.
The Galli nylon tapewounds were a warmer sound and lighter tension despite the same gauge. They took a bit of a left turn as they wore in. It was unpleasant. They were not a great match on the D4. They developed some weird overtones I can't describe but it made me sound like I was out of tune. That never happened on the RS88s.
Rob built and sent both D4s to me with the RS88EL set. Those two may be the only ones that didn't ship with the LaBella 760N set

And when I got the S4, he had the RS77 on it.