Skylab
Reviewerus Prolificus
With the clear glass, there is also a black-plate and a grey-plate Tung-Sol 6SU7GTY.
I actually have a couple pairs of Sylvania 6SU7GTY, which are clearly Sylvania internals. I'm assuming they are just a 6SL7GT with a brown michanol base, but they are a rare bird.
Try these:
http://www.ebay.com/itm/2-RCA-26-globe-balloon-matching-date-pair-UX226-UX-226-CX326-CX-326-equiv-/281052265578?pt=Vintage_Electronics_R2&hash=item4170053c6a
OR
http://www.ebay.com/itm/2-Cunningham-CX-326-26-globe-balloon-matching-pair-CX326-UX226-UX-226-equiv-/281051707585?pt=Vintage_Electronics_R2&hash=item416ffcb8c1
Good Luck!
The left looks like a Sylvania and the right like a Hytron.