Some tartans are available in silk. While I have not made a tartan bow tie yet, I have made bow ties from other fabrics. It is quite easy to do. Simply use an existing bow tie that is set to the proper length as the pattern. The tie is made in two sections and joined at the point that is at the back of the neck. Thus each section needs to be about 0.25 in. longer than when the two are joined so that the seem can be made. I add some extra material all around and then sew the two sections from the inside-out. I then use pinking shears to cut the excess fabric close to the stitches. The tie is then turned right side out and the sections hand stitched together. For the silks, depending on the weight, it will most likely be necessary to stiffen the tie with interfacing. I do not have much experience here, as I use stiffer fabrics. For wool, I would not bother with the interfacing. The thing to remember when making ties is that the fabric is almost always cut on the bias.

As for stained glass. I purchased a bow tie in Cambridge that looks like a window. Thus, just keep looking.

Rick