Another option currently sold by the foot: Nova Lite HP
Since many of the links in this thread have rotted and someone else might care... I damaged a line (my fault) and Hennessy replaced it under warranty. But before I worked that out with them, I found that Nova Lite HP 3/16" I can buy for $0.52/foot from http://rwrope.com/novabraid-novalite-hp.html and seems to meet specs http://www.novabraid.com/rope/novalight-hp.html 1459 lb tensile strength. I have no experience with the rope and didn't buy it after all due to the replacement, but it looks similar to what Hennessy use. Spyderline is still available but I see it only by the reel, not by the foot, so if you want less than a reel, the "Nova Lite HP" (N.B. "Nova Lite" is totally different) was all I could find by the foot. YMMV, no warranty, etc.