Yes. Lots of choices. However, as others have pointed out, a MIL or industrial number alone, does not guarantee that what you are buying is better. If it was made during the peak of vacuum tube production it will be better than towards the end of production. There were some common tube types, manufactured in the millions, that perform just as well as their more exotic MIL or industrial counterparts. I would contact Antique Electronic Supply and try some RCA 5814 or 5814A if they have them, especially if those tubes date from the 50's into the 60's. Not 70's. Other main stream NOS brands of this vintage would probably be worth a try. The 5814 draws slightly more heater current, but it should not be a problem.
There are other versions that were made to withstand various vibration levels, shock, voltage swings on the heater, and so forth that may not have anything at all to do with sonic performance. Some of these carry fancy numbers and fancy prices. NOS 12AU7's that are mainstream brands would be worth trying. Any tube produced in quantity probably achieved a fairly consistent performance level and stable quality in production.
