I swapped out some 2604s for LME49860s that I mounted on SOIC to DIP8 adapters. Worked well. The 49860 "only" has +/-22V rails, but because the maximum input and output voltages get closer to rail voltage compared to the 2604 they have the same usable range in practice. Not sure what kind of power supply you're dealing with but if it's a LM317/337 pair then it shouldn't be too hard to adjust the voltages down to 22V. Fixed regulators would obviously be a little more work and maybe not worth the effort.
As an aside, before I went the 49860 route, I e-mailed the company that is selling the 2604s in that e-bay listing (juried engineering llc) asking them to confirm the provenance of their op amps. The reason I asked is that photos on their site matched photos on other sites of obvious offshore fakes. I'm willing to bet that the fake sellers just grabbed the photo from the juried site, or everyone was just using a generic image that Burr Brown had at some point, but I wanted some reassurance. I never heard back from them so I gave them a pass.
