First I am not a hydraulic expert..
When I look at the spec's on the link you provided although the flow requirements are low the speed is very high
This single stage NorTrac® Bi-Rotational Pump/Motor has a low noise CBS6 bi-directional gear pump/motor allowing for either clockwise or counter-clockwise operation. Two check valves ensure safe, smooth operation in either direction. The light overall weight is ideal for all applications. GPM: 1.1, Material: Cast iron, Max. PSI: 4,000,
Rotations Per Minute: 3,600, Shaft Diameter (in.): 1/2, Shaft Type: Extended, Stage: 1, Usage: Continuous, Weight (lbs.): 5
2-piece cast iron construction for long life
CBS6 pump features 90% volumetric efficiency and 88% mechanical efficiency
1/2in. dia. extended shaft delivers 3,600 rotations per minute
Excellent cycle times
High power density
4-bolt flange with 1.78in. dia. pilot
Inlet and outlet side ports with SAE O-ring 9/16-18UNF
That is the rpm commonly found on water pumps and fans. Getting it slowed down would be a challenge.
Have you considered and rejected a hydraulic cylinder style which can easily be fabricated. A small hydraulic cylinder with an 8" stoke is cheap and durable.
This one on a 48" McKee/Kubota blower behind a B7100 has worked flawlessly for about 30 years. It was built using a surplus military aircraft cylinder which had a physical lock you could engage by turning the knob you see.
Dave M7040