The Sturmey 8W should work with your narrow dropouts. Do take into account that you'll have to go all the way down to a 30t chainring and 25t sprocket to get usable gearing out of it with 700c wheels.
Otherwise, the Sram 5 speed might be your best option without spreading the dropouts. It is 122mm OLN and has the same gear range as a Nexus 7.