Old school water slide decals generally used gelatin as the primary adhesive. You could try doing the same by improvising some hide glue. Heat up bit of knox/clear gelatin in water to about 140F . Smear a few drops on the tube surface, then apply normally. I've used this for similar stuff but not decals, so test on scrap. I bet it works fine.

There are also commercial decal application solutions that contain a small amount of adhesive. Check your local hobby shop.