DSF

I use white textile vinyls for printing basic logos and text but has anyone developed a white ink yet for Dye sub printing at a reasonable price .. or is it not possible for some reason ?

thanks

Textile inks rest on the surface of the material, sublimation inks are absorbed into the material itself as a dye. On fabrics white ink would serve no purpose, as it would simply be overshadowed by the darker colours of the garment and be virtually invisible. In much the same way a dtg can't print light colours onto dark garments without a white underbase.

you can't dye something to be a lighter colour.
To achieve what you're wanting on a tshirt, you need to use a white tshirt, and dye-sublimation print it black all over, except the areas you want white or other colours.