eBay

Here is a 50L6.

Various makes. All with Glass bottles. White boxed. Picture is of a 35L6. Sale is for a 50L6. Looks the same, different filament voltage.

Tested on a Jackson 648A or Hickok 533A and measured 85% or better.

Shipping in the US is $3 for up to 6 tubes via USPS First Class Mail. Will ship international, wait for invoice.

I accept PayPal and others, just ask.

If you purchase more than 1 at a time, wait for my invoice so shipping comes out OK.