Found this on Ebay for $349 + $30 shipping from WoodPRO out of Independence, Oregon. What do you think?
Here is what they claim:
This 8” spiral cutterhead replaces your standard straight knife cutterhead on many brand jointers including Grizzly, Sunhill, Pioneer, JET, Oliver, Wilke and many others. Each cutterhead has four spirals with indexable, four-sided carbide inserts, so each insert can be rotated 4 times for a new sharp edge.