Unfortunately the weather has been unusually warm and therefor very few (if any) ice climbing areas in good ice condition.
I would recomend taking a day on a glacier, you can find some decent climbs there but of course that’s not waterfall ice but at least you would get some ice climbing.
Sólheimajökull is the closest glacier from Reykjavík with an easy approach.
I trust that you don’t go unless you have enough experience and equipment to travel safely on the glacier. If not you can contact some of the guiding companies.
Hope you have a good time