SubstitutionsThese things depend a lot on how dominant the flavors of the wine vinegar or shallots are to the recipe.
Some commercial vinegar products are sold as "wine-flavored" vinegar. While I don't recommend them, they are essentially ordinary distilled vinegar diluted to normal strength with de-alcoholized dry red wine. If your recipe includes other liquids and if if will be heated to drive off the alcohol, you could try that. Use the amount of vinegar called for and an equal amount of red wine, decreasing another liquid by the amount of the wine. Obviously, this won't work in things like salad dressings where you're stuck with the residual alcohol.
If you can get wine and you can find vinegar that's not been heat-treated to destroy the "mother", you can easily make your own vinegar. I've done it (from red zinfandel, a grape with great fruitness that Ilike) and it's mostly just a matter of time, not skill. Unlike wine making where you must be careful to keep oxygen out, getting oxygen in is what makes the process go. You can find complete instructions at many sites by doing a Google search on vinegar making.
In any case, if you have to substitute a different vinegar, you'll just have a different recipe, not a bad one. I'd avoid distinctively-flavored vinegars, however, like apple cider or herb unless you think that's a compatible flavor.
If the shallots are a minor component in the recipe, especially one where they are cooked, I'd use an equal amount of onion with just a touch of garlic. I've made the substitution many times when we've run out of our home-grown shallots, and I was not hankering for a trip to the store. Again, even where the shallots play a bigger role, you will have a dish that tastes different, but still good.