AquaComputer offers a full cover Kryograpics Radeon R9 Nano Water Block. The design is single slot and might be just what the Doctor ordered.

First off, AquaComputer is based in germany and seem to be adressing just that market.  So if you like to swap out the original cooling solution for the NANO, Aqua Computer might have a nice alternative for you with their Full Coverage Water Block

The water block is based on exposed copper with an acrylic cover. The coolant channel flows over GPU and also the VRM area. The block itself is single-slot and thus easy to use for Crossfire of course. The product comes with standard G 1/4 fittings / threads.

AquaComputer was able to keep the NANO cooled at 35 °C with a 27 ° C water temperature while running Furmark. The block currently at pre-order, I do not have a pricing just yet. More info here.