Yeah, since they were only available through GW mail order they're probably pretty tough to get a hold of these days. I just did a quick google and eBay search (both US and UK), and none of them turned anything up.
I would post around various trade forums and see what you can dig up, though, if you're interested in them. I don't imagine they're especially expensive because I don't think there's very high demand for them, there just aren't many out there.