Tube kit for Nagra PL-L?

I suspect that Nagra test and match these tubes to standards significantly above what you're likely to acquire off the shelf.

Nagra burns-in THEN critically grades the tubes to a super fine degree (color coding the tube base red,green or black depending on noise level).

Sure you can roll your own, and have had many owners successfully, and to rave reviews, use NOS tubes. The PL-L has just 3 tubes.

A typical Nagra tube kit may contain three different brands, but usually Sovtek and EI.

Nagra introduced a cheaper "Dealer" tube kit that is just a cardboard box with the three tubes, selling for much cheaper than the alternative. That is a deluxe kit with Nagra gloves, wrenches and tubes, enclosed in a nice clamshell case with foam cutouts for a bit more.

Disclosure: I used to be their US Service Manager.

Some good tube dealers also burn in their tubes then test them above and beyond the manufacturers testing. Jim McShane is one such dealer. You can find him over on Audio Asylum or a simple search. I sure there are others do you know which tubes are involved?