I built my own, and am very happy with it. There are certainly choices for purchase.
Before buying, consider the hydraulic hook up. If you're using the third function valve, that's fine, but know that you won't have the detent return feature, you'll have to lever it to split, and to retract. Be cautious about using log splitted type detent valves on the tractor system (you click past a detent, and the splitter returns on its own). I started out with a detent type log splitter valve as a third function valve on my JD650. It worked, except for one problem: There was a combination of motions where at the top of the lift stroke for the loader, the third function valve would sense and release pressure, and drop the loader like you'd just floated it it - super dangerous at all, but worse when it was high. I contacted the valve manufacturer, and they said that was not a usable valve on that type of hydraulic system, use a regular valve, and lever it both ways. So I did, and it works.
Also, if you use a valve which is not from the tractor manufacturer, it may have a built in pressure relief, set lower than the system pressure on the tractor, so you don't get the muscle you expect. I spent a frustrating winter sorta splitting, to then connect a dump trailer which would not pump. When I figured out the problem, and reset the pressure relief in the third function valve, the dump trailer became a slingshot, and the log splitter would now do the really hard knotty maple no problem....
My new JD1025R has the factory third function valve, and it works a charm - for the $$$$!