printing color decals for fusing
I have recently found the following product which may be a substitute for what you want here
note that it is only baked in a regular oven, but I am sure you can come up with something to design a decal on a single sheet of glass – I certainly can.
Alternately if you want something standard, ceramicporcelain decals are high fire products and can be purchased ready printed at your local ceramicraft store.
Good luck & enjoy glass