Several methods assume direct access to the DC motor inside the trolley. This allows direction reversal by simply reversing the DC voltage polarity on the track; we can deal with how you make DC track voltage from your ZW later. Your bump-n-go requires the mechanical bumping which moves a slide switch inside the trolley to perform this DC voltage reversal.
So the question is are you willing/able to do some minor re-wiring inside the trolley? It most likely will involve soldering which I realize is not in everyone's comfort zone.
As for your in-hand occupancy detectors, I'd think you need one on each end of the line. Hence at minimum, if using the 153 IR, you'd have to buy a 2nd one which is $30 or so. I couldn't find an online description of the IRS-2 much less a company website; these cottage-industry widgets usually come in a stapled bag with a one page "manual". If you are able to scan/photo the instructions or provide an online link to the same we can see its relevance.
In any case, the guys above have given a wide variety of off-the-shelf options. This is a problem that has been solved! I approach it as a re-invent-the-wheel exercise while sheltering in place. I think it could be done with, say, $5-10 in components/modules for a DIY enthusiast - meaning guys that turn on the soldering iron and coffee pot at the same time each morning! 
