I think what is usually recommended for silk ties is fusible nylon tricot. JoAnn's had it in small one-yard packages a few years ago when I looked. I would advise experimenting with it first to see if you like the results. This fusible adds a fair amount of bulk to the silk. A knit fusible like this has the advantage of having a little stretch to it. If you need a lot of it, it's cheaper to purchase it online; I bought yardage from a drapery supply company (I think it was Brown & Sons).
There may be better fusibles for silk, but this is the one I saw recommended in a book about silk tie quilts.