on average the gaskets use to be about $80.00 to $130.00 plus shipping. you can expect to pay $130.00-$170.00 plus shipping or including shipping depending on where you go now if you do find one being that there are supply and demand issues.
looks like its either pay the piper or wait it out until production kicks back in.
looks like rick has what you need for around $110.00ish plus shipping.....plus you may need to purchase a lock strip which I think is about $20.00
BUT I do believe rick offers FABO member discounts so you might be able to save a few bucks!
here is a link.....and I don't see any highlights saying he is out of stock so you may be in luck!
http://www.laysons.com/Catalog.cfm?nCatID=2096&nModelID=5&nModelYear=1973