Hi you can make up an identical trolley by getting the parts from any shop such as bias whitworths etc and you can use better quality bits such as spectra rope, high quality stainless fitting, bungee cord. My setup consists of 2 loops of bungee cord ($2.20/m), 2 stainless quick link shackles ($4.85 each), length of spectra 3m at $2/m, stainless snap hook $4.99. this works great and slides easily up and back I run the anchor line through snap hook and then put a stainless ring on to act as a stopper by looping the line through the ring. I have attached some photos and the finished job looks very similar to the one you show. I also have one on the front as well as i find when working ledges rips and drains that getting the bait/lure working with the flow is more successful