Vinyl/plastic does not last very long, especially when abused or out in the sun. As for your question, Lowes, Home Depot sells the sections. Depending on how long the gate is, you may have to use a fence section, and place a wheel on the bottom.
Actually, good quality vinyl fence holds up better than wood because it includes anti-UV material right in the vinyl. Wood can warp and rot, but vinyl is stable. We sell 6 and 8 foot drive gates online in eight styles - have a look at http://www.nationwidevinyl.com/Picket-Fence-Gates.html
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