I haven't priced the oem, but one option you might consider is installing some factory RZR seats in your Prowler. You can often find deals on a set (whether it be locally, Craig's List, or eBay). They are pretty easy to adapt to your AC seat base, and pretty comfortable. You will have to take off your rubber head rest pads to fit properly. Just an option if you can't find oem Arctic Cat seats for affordable.
-2011 Polaris RZR-4 800 (SOLD)
-1999 Polaris Sportsman 500 ATV
-2006 AC Prowler 650XT (SOLD)-- updated bevel gears, updated oil pump driven gear, 4 wheel disc brakes, line lock E-brake, Papa Slap clutch, Xentec HID's, Dynatek CDI, Warn skid plates, Intellitronix gauges, 2010 intake/cvt duct work and dust shield, RZR seats, Bestop folding windshield, full cab kit, rear cage and rear seats (4 seater)