Hmm... Right off hand, I can't provide a source for 0.015" pillow ticking. With apologies, I'll suggest alternatives.
Track of the Wolf has top-quality 0.018" ticking in pre-cut patches, but also in 1-1/2" x 36" strips and in half yard bulk pieces. This is thicker than you requested, though.
Track also has 0.015" plain cotton in the same configurations: pre-cut patches, strips, and half-yard sections. I think the fabric is "pocket drill," which is used for trouser pockets, so you know it is tightly woven and tough.
Personally, I don't think the blue stripes make a difference. However, I also understand that if you have your mind set on something, nothing else will do. I'm thataway myself. Might I suggest getting a half yard of the 0.015" pocket drill from Track and trying it out? Just to keep you shooting until you find what you want. One thing about the patches you get from Track is that you can be confident they are all cotton... No polyester to melt and build up in your bore.
You might also check The Gun Works and October Country. I hear both outfits have good patches, although I have no personal experience with them.
Good luck, hoss!
Notchy Bob