Hi,
I'm not a regular minis gamer, but I can answer a few of your questions. No one is currently making Tekumel miniatures. There was a guy operating as PHD Games, but he's has been unresponsive to email for a long time (even though his webpage is still up). He also lives (lived?) in or next to New Orleans, and may well have been flooded out this year.
As Mark noted, there are some folks talking about getting some new miniatures produced for Tekumel. Check out the archives of the main Tekumel yahoogroup:
http://games.groups.yahoo.com/group/tekumel/
Also, there is a recently created yahoogroup specifically dedicated to Tekumel miniatures and war-gaming.
http://games.groups.yahoo.com/group/TekumelMinis-War/
There's a nice collection of photos there, as well as more people interested in wargaming than there are here.
My sense regarding Barker's use of "phalanx" is taken from his essay on formations. He seems to use it just to mean a body of men in close order, usually a square or retangular formation, most often of heavy infantry, probably armed with pole-arms. There's definitely no specification of the number of men involved.
I agree with you that it would be great to have some "cardboard heroes" for Tekumel. No one has undertaken this idea, but I think it would be a good one.