If the original blades are brazed onto the crown, you should be able to have the old blades removed and new blades brazed on by a framebuilder. If you can find suitable SL blades already fabricated (with appropriate rake, dropouts installed, and the tubing shaped and dimensioned for the crown lugs), it shouldn't cost more than a couple of hundred dollars, about the cost of replacing a top tube or a down tube.

If the framebuilder has to build up the blades, it'll be more expensive.