Tires and wheels certainly are not specific to the TRX300, other than maybe the OEM tires and wheels. But there are some old school tires and wheels that look great on 300's, just fit with the era the machine was made in. Here's a few I like.
Spun aluminum wheel with a billet center. One of the first "fancy" wheels for ATV's with it's billet machined center. These predate cast aluminum ATV wheels. 12x7, came in polished or later black paint. Late 1990's early 2000's. This wheel has been discontinued for a long time, and is quite difficult to find now.
Vampires were one of the first MUD tires for ATV's, and the EDL was at one time just about the baddest thing out there. 28x10x12 although they measured about 27" at best, 2" deep lugs, one gnarly tire. These dig HARD but don't paddle well. Still available today, although only made in USA for the first few years, these USA made EDL's were for a long time regarded as the best EDL, due to the fact that they measured taller than the Mexican and other EDL's.
Current sizing as follows:
The Mud Machine Bi/Tri Combo was a great mud tire setup that has also gone the way of the dodo. Made by "Sand Tires Unlimited" The most popular size was 27" but was also offered in 25" and 26" sizes. Check out the link below for even more info on this old school tire.
12x7 Steel wheel came in black, silver, chrome, and chrome/black center. Now only available in black and silver in 12x7 and 14x7.