I don't think there is a way to put power steering on value model sportsman, the XP's are the only ones that the EPS unit will bolt into and work with the electronics the XP has. Nothing aftermarket as far as I know.
Mine- 2011 Sportsman X2 550 With EPS!!-Warn 2500lb Winch, Guru Brush Guard, RZR H13 bulb headlights, KC LED Yellow tint Driving Lights, Rigid light bar mounted in the pod, Autometer Phantom Oil Temperature, Coolant Temperature, and Voltmeter Gauges, Polaris Low Lock and Ride windshield, Acerbis Handguards, Symtec Heated Grips and Thumb warmer, 2+2 gallon Rotopax Fuel packs, STI HD Beadlock wheels and 27" GBC Spartacus Tires
Hers- 2012 Sportsman 550XP EPS Blue Fire LE 27" ITP Mudlites on ITP SS212 Wheels, LED headlights, Mile Marker 2500 lb winch, Polaris bodyguards