Balsamic vinegar replacement
I second petals suggestion: wine vinegar and a little bit of sugar.
If red or white wine vinegar is not available (can't remember, lived in India for a year in 1996) then any vinegar with a little sugar, but remember that rice vinegar is not nearly as acidic as wine vinegar.
You might have to look at buying some decent wine and turning the left overs into vinegar (great excuse for buying wine :) )
Life is too short to drink bad wine