You will need a 2HP to 3HP electric motor and a 12GPM pump ... plus hoses, two-way valve with center off (splitter valve). I don't know where you would buy one all set up for our purposes. Such a power package would run probably $4000 or more. Many are gas engine powered.
If you want only 3" of travel, you will have to engineer that in the build with a pressure stop or electronic control.
You really need two hands to use a press safely, so some form of foot control is needed.
James Batson's book on building a hydraulic press is a very valuable resource.
Also, there are dozens ... maybe hundreds ... of build threads in Shop Talk. Just use the Custom Search Engine in the stickies and search "Hydraulic Press" and "Hydraulic Press Build"
I want to ask about your skills and ability for this build. Building a forging press is a lot bigger job than most folks realize. Besides some serious welding and machine work skills, it will take some serious equipment. Also, there is no scrimping on a press build. Try and save money by using lighter materials and it will tear itself apart.
Do you have a pretty good machine shop with the ability to cut and weld large I-beams?
Do you have a large welder capable of doing structural welding on 3/8" to 1/2" steel?
Does your shop have the ability to lift the frame as you weld it to the base with the frame weighting maybe 400 pounds (or more)?
Does your shop have, or can you install, a dedicated 220V 30 amp circuit?
Take a look at the Coal Iron Press as well as some of its competitors. It is a turnkey package that is hard to beat without a lot of welding equipment and experience.
They also have a benchtop unit that is really nice and even cheaper. Ken H has one on a rolling Kitchen Cart.