In Canada, Mountain Equipment Co-op now sells them;

We're still in the early spring freeze / thaw cycle here, and steep hills can get really gnarly...these puppies work great in the woods! Last week I went for a run in the bush and didn't break my stride even when crossing frozen sections of the trail including corners, and going up or down hills.

Good idea about using carbide tips on the spikes, Evan. I had intentions of contacting them about that but never did, so now I'll follow your lead and give them a buzz too.