[Mr.T]

It's still possible to purchase newly-manufactured reel-to-reel tapes
in that size. The Quantegy company (formerly a division of Ampex) is
apparently the only company in the world still making reel-to-reel.
They have a couple of different formulations (406/407 is said to be a
general-purpose budget formulation, and 456 is their "Grand Master"
high-end tape).

Ironic isn't it that Ampex 406/407 was the biggest cause of the problem
originally.
At least the binder formulation has been changed :-)

MrT.