Hello Pug, welcome aboard.
Just thinking out loud...if the blades are not available and you end up paying 2 or 3 times the rate of retail knives...it may not take long to justify a more recent 6" jointer. About a year ago i paid $100 for a Delta variable speed bench-top, which i sold last weekend for $125 because about 6 months ago i found a Grizzly long-bed for $100 on Craigslist. In both cases, the knives they use are still used in new models so they are easily (and relatively cheaply) available.
Compared to custom-making knives, scouring Craigslist (or ebay if you're lucky enough to find one in driving range) may be a good investment. All that goes out the window if you have an emotional attachment to the tool--and that's understandable.