One of the things that have stuck in my head from last August's Hops Academy put on by the Haas company, was a hop-derived product called Lipohop c-plus. It is a completely natural extract from hops that provide foam control similar (I assume) to the silicone based products. I looked into it as I don't like the idea of silicone in my beer, but they only sell it in 10 kg containers. Their info here: http://www.barthhaasgroup.com/johbarth/images/pdfs/Lipohop_en.pdf
Fast forward to this week. I mentioned this to a couple of great guys opening a LHBS here in Yakima. They emailed me saying they were going to get this from Haas and sell it in homebrewer sized doses (~3 grams per 5 gal.). I'll keep you posted regarding availablility and my experiments with it.
FYI, here is their website, though nothing is there about this yet. http://www.yakimavalleyhops.com/default.asp