I highly recommend felt-soled boots for anything except boat diving, they're slippery as heck on fiberglass. I use 5mm felt-soled boots in Hawaii and wouldn't go without. They can be bought at Walmart and Kmart there, though selection is chancy, and some of the dive shops carry them. Deep See is one of the brands, Aropec is another. My preference is to stay away from the Tabi-toe fisherman/stream style, I find the toe divider rubs.
I'm a little surprised they aren't more common, maybe shore diving from rocky areas just isn't that popular.
Hard felt soles are available as a DIY for fishing waders. I glued a pair of those on some dive boots once and they worked fine, though you can end up with a pretty thick sole that way, and it may not fit your fins. The commercial models have typical sole thickness.