I know for sure, that the last time we stayed at the Polynesian they had the "beach" wheelchair for the zero entry pool. This pool was very accessible.
At the Beach Club, there is a zero entry pool, but that area of the pool is essentially a just a sand play area for children and only about 2 feet deep. After our complaining about the lack of access in October '06, we have been recently informed that they now have a beach chair. But that is not much help for a grown man who doesn't want to just play in the sand. We have not had any replies concerning our questions about lack of access to the other areas of the pool.
I would think that all of the resorts with zero entry pools now have a beach chair, but I would check on that.