Get some rounds on your P bass. Broader frequencies are then available - a little goes a long way - and you can dial it back if it's too much.
Also, support the soloist by playing a little bit more - some double stops to help outline the chords - the odd harmonics to do the same and add interest or flavour.
Most of my playing recently has been with a guitarist pal of mine and yes when he takes a solo, it's just me left being the band. To be honest, it fits well with my own style - I've never been one to hide away at the bottom end but I have to say that audiences tend to like it and I constantly get comments about how refreshing it is to hear someone playing "up front" and how rare that is these days.
So consider giving it a go - to my mind this is more about mindset than effects pedals.