Those old hoods are like golden hen's teeth; it's ridiculous that they're one of the most perishable items on a bike and nobody makes durable replacements because they aren't generic enough.

I have both Campy Super Record levers and Shimano 600 levers from the mid-80s. Comparing them side-by-side, it looks like the hoods would be swappable. I mention this because there is an outfit called Euro-Asia that makes Campy knock-off hoods in gum-like brown and black. No logos, somewhat crude, and a mold line down the middle, but they might fit your levers. $20 on eBay or at Lickbike.com, slightly more from Peter White, and other places too.

I have a new set of Campy levers coming from an eBay purchase, that have these replacement hoods on them (I'm too cheap to pay $70 for the real thing); when they get here, I will try them on a 600 lever, and let you know how they fit.

Another option is to buy a set of NOS levers with hoods; there are several on eBay at a time. That runs you about $40-45.

In the end, we who love bikes of the non-aero gum hood era will need to find some DIY way to refit brake levers with something cushioning, that will last for awhile - like pliable and resilient papier-mache'. There's a product made for roofing called RD Elastoflex that a representative gave me a sample of -- in theory it seemed ideal. It's a reinforced acrylic (using woven polyester mesh, I think), very flexible when cured but tough, that might be applied carefully by brush over a lever body protected with food wrap or heat-shrink, or even low-tack masking tape. If I can get a can of this stuff, I may try it out.