I've had a lot of luck through a place called rockauto.com. They seem to carry about everything available for Isuzu's (not from dealer). I've ordered a LOT of stuff and it's been high quality and great prices. I checked for the half shafts and they have them listed for $90 plus 100 core charge. Plus there a different part number than same year Trooper. Check it out. Hope this Helps.
Dan
Dan