There is a bike rental in Å i Lofoten. The prices are extremely high. I barely managed to rent two bikes for half a day. I remember the cost for a full day bike was around 500 NOK. Also the bikes were not in a very good shape either. The owner was also rude.
I don't know if there are any other bike rentals in the area though. Try negotiating as tough as you can, because he won't rent all the bikes in one day.