There are a few mass produced alternatives to cork that are available, but none of it has made the cross over to fly fishing. Some of the high quality EVA handles used on the top carp and spinning rods are warm to the touch, offer superb grip, transfer a lot ot the rods "feel" to the hand and are exceptionally hard wearing..but they are black and look like rubber, so I doubt fly anglers would ever be receptive to it.
There are different qualities of Duplon handle, some soft and squishy as MAgnus says, but some quite hard and dense, with a feel very much like cork..but those are expensive. I got some from Japan and they worked out around £20 each
before postage..but they really were very nice indeed. They could be shaped just like cork and had that very slight compression that good cork has and not that much heavier.
As for the quality of cork, well, the demand for high quality wine corks had plumetted and so cork farmers have had to diversify to stay in business, and this means supplying the building trade with a lower grade of cork for tiles, floors etc. The rod trade has always got the surplus from the wine cork trade (hence sometimes supply was hard to find) but these days the handful of wine cork producers have very little spare. Gone are the days when every valley in France had a cork farmer for the local vineyards....as cassies dad found out. He owns a vineyard and has reluctantly gone over to cork composite corks..if that makes sense??
