Try it the old fashioned, natural way.
If you use fresh grapes - Try maceration. Crush the grapes and allow to sit on the skins for a longer period of time. You might also want to try adding the grape stems during this process.
If you do not use fresh grapes, try adding good quality oak beads. This brings tannins to the party, but also provides a lot of beneficial flavor compounds to the wine.
johnT.