The (sort of) attempted wrapped gut-like D and G strings of the RS4000 set, as played by Herbie Flowers on Walk on the Wild Side etc. Nylon wound on nylon, very low tension and - depending on your bass - may need to be double wound around tailpiece so that the silks don't encroach on the bridge (I had to for my old German 3/4).
Stringsdirect sells for £92 for the pair, how about £42 posted in UK? Been on my bass for only a few hours, home only playing time.