Wine Vinegar!
I love vinegar to sour things and use a lot of it. I buy Bragg organic, raw, unfiltered apple cider vinegar with the mother still in it. It's a lot more expensive than regular vinegar, but what I do is when the bottle about 1/4 full, I top it up with leftover wine and let it set for a week or so, then have a nice big full bottle of pino grigio or whatever was leftover, vinegar. Get a couple bottles so you can have different flavors going. As long as you let it sit and mature, you can keep a bottle going for some time since the mother is still active and your feeding it like a yeast.