Many NOS tubes are very good, but the can get pretty pricey. At least you are only looking for a pair, which helps a lot. The NOS market can be scary and dangerous if you don't know what you are doing. Pricey, but some shady re-sellers out there.
For new tubes, I have found the Psvane tubes to offer very good quality at reasonable prices. Of course, as always, YMMV.
For new tubes, I have found the Psvane tubes to offer very good quality at reasonable prices. Of course, as always, YMMV.