The creator of the often-praised 4-Lane electronic finish line, 3DBotMaker, has officially release a 2-Lane version. It's available for purchase now from his Etsy store for $40.
I reviewed the 4-Lane finish line back in the Spring and it is a great product. Simple, sturdy and works perfectly with all that orange track you have lying around. Several other RLD members purchased the finish line based on that recommendation and there haven't been any complaints.
3DBotMaker has a short list of great accessories for racing, including a starting gate, connectors and some funnels.