What do you think would seem like a reasonable price point? My friend considered making them, but concluded the market was likely too small and that if they were popular people could knock them off pretty easily. After seeing his PVC "Model 1", I made 2 for PAPA with about $20-30 in parts from Home Depot and an hour in a shop with a bandsaw, drill-press and sander. I think his later all-steel/roller-blade-wheel model had a parts cost around $30-35, and required a couple of jigs for drilling and tapping the holes. It does have the advantage that the prods can be closer together, which makes it a bit easier to handle.
For the PVC model, you can buy the smaller diameter black pipe pre-cut to a reasonable length, the PVC you have to cut yourself. The prods are simply threaded bolts wrapped in a piece of bicycle inner-tube and electrical tape (which I'm not sure is strictly necessary, as the later models didn't do that). Both the black pipe and bolts go all the way thru the PVC pipe, so the only hard bit is drilling the holes straight/parallel. The prods are only as far apart as they must be to provide clearance for the pipe. Basically in the middle the 2 bolts and the black pipe are touching. I recommend 1/4" Grade 8 (hardened steel) bolts or stainless that are threaded along the whole length. I drilled a hole diameter small enough so that the pre-threaded black pipe and bolts would cut threads into the PVC (and snug up nicely). You have to ream out one side to a slightly bigger diameter to clear the unthreaded part of the black pipe which is slightly larger diameter than the threaded side. A scrap of carpet can protect the floor from bolt heads if you want to use on hardwood/tile.
Given that pins are tippy 4-legged things and WMS's long tradition of cows, the device was called a "Cattleprod".