[Closed] Bib shorts for warmer weather?

I suffer from lower back issues and find keeping my it away from the elements helps me in avoiding too many problems associated with cycling.
Before you start replying with helpful advice like stretching/yoga. I do all these things and stretch daily, as I spend my working day mostly sat at my desk.

In the winter months I wear bib tights which keeps my back nice and toasty but now I find I'm over dressed now it's warming up.

So to my question, I'm after some lightweight bib shorts that are suitable for spring/autumn riding. (Summer I can get away with just a liner, if it's a warm summer that is!) What do you regulars on STW recommend?
Cheers in advance!