This model site has Silkspan and some cool supplies.
http://www.easybuiltmodels.com/parts.htm
I ordered a roll of the silkspan from easy built models. It has not arrived yet. When it does I will let you know what I think of it.
Here in DFW there is an old (very old) hobby shop in Irving called Model Aircraft Labs (M.A.L. Hobby Shop). The place has been there for something like 66 years. You could talk to the owner all day about the good old times. I had not been there since 1998 or so. Last week I called him to ask if he had any silkspan. He said yes so I went over there to look at it.
This looked to be the original silkspan, still in the tube, medium weight, maybe a bit heavier. He also had some light weight. This silkspan was a pale beige color, not white. I have no idea how old it is. It was in excellent condition so I bought 10 sheets of what looked to be medium weight.
The shop owner told me that he heard about the silkspan shortage. He thinks it is nothing more than low demand so there is no reason for producers to make it. Maybe the tea bag makers found something else (a cheaper material?) and since there are not enough modelers who actually build these days, silkspan is not worth making. Who really knows the real reason why?
This shop was the only one in DFW that I called or visited that had any silkspan left. If they had none, they said they did not know where they could get any more.
This shop is a trip back in time. It is a small place crammed with things I last saw 40 years ago. The shop owner (son of the founder) said that Dick Mathis used to get his balsa there. He keeps some balsa on hand but not as much since things have changed so much. He still has some jars of original Aero Gloss dope. Hanging from the ceiling are are all sorts of planes. Some of them are free flight planes, maybe some by Dick Mathis. There was a plastic Corsair with a Wen Mac .049 and the old Cox trainer, the blue and yellow one with the rubber bands to hold it together.