Actually wood flooring often comes in those lengths but in a three season room I would be tempted to use luxury vinyl plank for a litle bit more warmth.

In a 3 season room, vinyl has problems (shrinks, cracks, etc). When it comes to uncontrolled "indoor" spaces (very warm in summer and very cold in winter) we need to move away from "indoor" products like vinyl, wood, etc. Vinyl "shrinks" and curls in areas that do not have humidity control. Vinyl will also "burn" in direct sunlight as well as "warp" if it heats beyond 85 F (a pool of sunlight on a vinyl floor = 100F or higher).

The "outdoor" options are what you are down to: pressure treated wood (as for outdoor patios); porcelain tiles (so long as water doesn't freeze on them the should be fine); indoor/outdoor carpet; concrete, stone.

If the "look of wood" is what you are after, you might have to bite the bullet and work with porcelain tiles (the longest lasting, easiest to maintain product) or pressure treated wood for decking material (stained, etc). I don't think you are looking for carpet, concrete or stone.