Blackfeather has been gone for months, but Batterystation had some cheap LR44's. They're alkaline, not zinc-air.
Beam_me_up, the Keymate is brighter than the Arc AAA when the Keymate's batteries are brand new. Once it's been running a little while, it's dimmer.
It's a well-made metal light and some people like it a lot. More power to 'em, if that's how their tastes run. Me, I see the Arc's AAA battery and long, (semi) regulated runtime as a huge advantage. If I want to use button/coin cells, I prefer the Photon-style CR2016 lithium lights to button cell lights like the Keymate. They're a lot smaller/lighter and they work just as well and their runtime is comparable.
Peak now has a light that seems intended to be an Arc AAA successor, though they don't call much attention to it. See their homepage (
www.peakledsolutions.com ), click Annameria Dallasandra collection, and see where it says 1aaa lug-style light for $24.95. I think it will be set for lower output than the Arc (engineering difference) but should run somewhat longer.
Here's a link to Roy's graph of Keymate output. See that it's down to 50% after just a half hour. For an Arc AAA, that would be more than 5 hours.
http://ftp2.itexas.net/Rbost/key-mate.jpg