I am putting this here because I was wondering about this before I came back to Bergen today but couldn't find the answer anywhere -- especially not on Norled's website !
There are lockers at the ferry/expressboat terminal in Bergen (for example if you are taking Norled's Expressboat to Balestrand, Bergen, or Flåm).
My flight arrived at 11:30 this morning and I planned to take the 16:30 ferry to Balestrand this afternoon. That gave me a few hours to have lunch and do a couple of errands in Bergen, which I really wanted to do without my suitcase and my backpack.
Well, the Strandkaiterminalen / Norled building has lockers at the far end, two different sizes. There are central machines on each side that control the banks of lockers, and English is available on the machines, so it was easy. The big locker that I used was 70 NOK; the smaller size was 55 NOK. That rate is valid for 24 hours, if I remember correctly.
Anyway, in case anyone else ever wonders or searches : left luggage lockers at Norled ferry terminal in Bergen ! Easy peasy.