La Bella 760N-S Black Nylon Tape

I purchased these gorgeous black strings for my walnut Ibanez MikroBass to emulate the upright bass tone.
The looks were amazing!
Feel under the fingers is soft as satin and the upright-like bass tone is definitely there.
At home (old electricity) I did get an annoying hum because my fingers didn't touch metal while playing. A problem that didn't occur in music school (newer building).
Furthermore I wasn't very happy with the sound of the nylon string on the frets, so I changed back to flatwounds.
For a well-insulated fretless bass, these strings might get you as close as anything to the upright vibe.
And they will probably last for years and years.