You can get the military 6n15n-ev's here, from the Decware catalog. If you scroll down the catalog page, you'll come to a tube replacement link near the bottom. They're $15 apiece, which seems pretty good for a onesy-twosy type purchase. As you've noticed, you've got to buy quite a few before getting the price down much lower, (plus you would also know Decware is a superb place to do business with).

There are also a few cryo'ed pairs available in the Decware classifieds for $22 apiece; which is not a screaming deal on the one hand, but not unreasonable, again, for onesy-twosy purchases.

Karl