EBAY has a few belt driven pumps like the ones mentioned above. Do a Muncie search and you will see them. They are around $400. But like said previously you will need to fab mounts. A portable gas unit would need to be at least a 11-13 hp Honda to provide a decent flow. It would still be much less output then the original PTO but would suffice. This is exemplified by the hydraulic power sources used for Stanley/Fairmont portable hydraulic tools. Their gas power supplies are in the 16-20 HP range and put out 6-8 GPM at 2000 PSI. The belt driven clutch pumps have a higher output then you would get with even a 20 hp gas engine, if you get the larger models. PH11 puts out 14 gpm at 1500 rpm and at 2000 psi. There is a one size larger then that but the PH11 model is a popular size.
You can make a system yourself, look at this site, I have used these guys for years.
https://www.
surpluscenter.com/
They also have a tech info area that has formulas to figure out the flow and pressure you can get from various pumps, and the HP needed to run them. They have aluminum mounts for mounting a gear pump right up to a Honda or other gas engine, hydraulic tanks, gear pumps,filters, fittings etc. But what ever system you use don't forget to install a relief valve. Buyers and Prince are good entry level USA made brands for hydraulic valves, tanks and accessories.
To make your own system you would need either a engine mounted belt driven pump or a dedicated small engine with the mount for a gear pump sized to your engine's HP. A hydraulic hose going from the output of your pump to a relief valve. You will need an open center lever operated directional control valve. A hydraulic line from the relief valve outlet to your pressure port on your control valve. You will need a hydraulic tank and a filter mount with filter. A hydraulic hose coming from the tank to the pump's inlet. You will need a hydraulic line coming from the relief valve's over flow/over pressure port then back to the tank. You will need a return line from the open center valve to the filter inlet then from the outlet to the tank. Then you will need two hydraulic lines from the work ports of your open center valve to the winch. You can also get a control valve with a relief valve built into it.
So to recap, if you have a open center,remote relief valve system, you will have 3 connections at the tank(2 inlet 1 outlet), 3 connections at the relief valve(1inlet 2 outlet), 2 connections at the filter(1 in 1 out), 4 connections at the control valve(1 inlet,1 outlet and 2 work), and 2 work connections at the winch. Thats a simple but a complete system. Set the relief valve at the same pressure the winch system is. That way your pull rating will be the same but it may just be just slower.
