If you are in the USA you don't have a 89 model 4x4. They were not sold here in 89. That said, you can order a new OEM fender off partzilla or rocky mountain atv. You just need your year and model number. If they arent available for your year you can use any front fender from 88-00 but you will have to drill out the fender flare holes as they are different.
Good luck finding a new fender. Everybody caught wind that they were getting scarce and basically they were bought up by collectors. If you want some you'll be paying big bucks. I would just find a fender the same colour off another 300 and use that. They are all interchangeable (tanks are not though). Like LBZ said the only difference would be holes for the flares. The 1989 300FW does exist, just not in the USA. It was sold literally everywhere else but.