Vitus decals are easy enough to find, but Avanti decals might be a different story.
You can always fall back on the option of just turning the bike into a "generic" Vitus 979 with just a widely available Vitus decal set, but I can understand why one might want to retain the more unique Avanti branding. But sometimes you might not have a choice when the decals are already "unobtanium".
If the Avanti fonts are pretty standard, you can also just have decals custom made, but it will cost much more to do so.