They're already epoxy coated, but I've been told that the coating is pretty thin and chips easily. I personally am going to take aquarium silicon and rub it around the magnet so that it's a little thicker.
levon, I'm not finding anything else yet. As far as I can find that looks like what we'll be using.
I think i'll be ordering 50 of them for $62 + $9.19 s/h. That's $1.43 a magnet. so $2.86 a pair. If your glass is so thick that you need to double them up then that makes them only $5.72 a set. Still cheaper than frag-mags slightly. Don't konw how much frag mags shipping is. But I bet it makes them out to be about $7.50 a mag give or take a few cents.