I've found 3 tubs that you might be interested in. They are all brand new, unused, never fitted, although they have been in storage for a few years.
The first one is a Continental Competition GP tanwall, which is marked as 26 x 3/4 (so 19mm).
The second one is a TUFO Jet 26" Pro Tanwall 19 mm.
Third one is a Vittoria Corsa EVO-CX this is all black and is 26 x 20mm and has a Kevlar anti-puncture casing. A very nice tyre.
I'm looking for £25 each for the Conti and the Tufo and £30 for the Vittoria. Plus postage.