La Bella are very good for a regular flatwond sound.
Thomastik makes “Jazz Flatwounds” that are a bit different. The strings are lighter than most, and teh low strings have a bit of space between windings. (Apparently they wind a very fine wire alongside the flatwinding and then pull out the flat one, I think.) They sound different and not as dead as normal flats, but I couldn’t get used to the tubby qualities that the light gauges caused. Some people lke them.
Pyramid Gold are reputed to be very good (and very expensive) and supple like Thomastiks, but with more normal gauges. I bought some but I couldn’t get them to work at all because the cloth windings ran over either my bridge or my nut.
God damn, I’ve gotta start playing my bass again. Maybe get a new one. I have one poplar P I got in middle school. I played around with flats a bit. I also want a neck-through bass, maybe a Carvin. Really 3 basses, one round, one flats, one fretless. I don’t even have an amp now.