The Honeywell sensors are at http://www.ssec.honeywell.com/magnetic/
There's a section specifically on compass applications.
Two UK distributors are www.tdc.co.uk and www.inertial.co.uk

Fluxgates
The trouble with putting "Fluxgate" into internet search engines is you get loads of "chaff" about people who have used fluxgates, manufacturers of fluxgates or fluxgate-based instruments, etc, but few actual useful hits about fluxgates!

But here are the references I promised:

[1] Richard Noble, Electronics Fluxgate compass
Electronics World + Wireless World
Jan 1992
This cites an earlier (Sep 91) article, which might be what Steve was thinking of?
These articles are quite widely cited in The Literature on the net.
The company quoted for supplying the cores used in the article no longer exists, and their successor has not replied to E-Mails. :-(

[2] John Beale, "A Simple Fluxgate Sensor"
http://beale.best.vwh.net/measure/f...index.html
Based on [1]

[3] Compass Points Iss 5 Sep 94
http://www.chaos.org.uk/survex/cp...5.htm#Art1
Provides some comments on some commercial products

[4] Robert C. Snare, "A History of Vector Magnetometry in Space"
http://www-ssc.igpp.ucla.edu/personnel...story.html
A comprehensive review, with extensive bibliography.

[5] Steven Gill, Glynn Lloyd, John Mitchell, "Investigation into Fluxgate techniques using torridal [sic] coils"
This excellent report seems to be the result of an (undergraduate?) student project.
Unfortunately, I can no longer find this one on the web. :-(