I've been looking at this too. Surfing the net has located a number of digital electronic counters, but so far none I've found has been both suitable and cheap enough to be attractive. I don't know whether the Nordic component can be gotten as a purchased item. If it is available, it still needs a handy bike-mounted switching device, as do all of the other electronic counters on the market.
Thus far it looks to me like Neville's approach remains the most attractive option. It all comes in one package and the price is right. I use it now, and find that it suits me.