It's such a small amount of brandy (1/4 cup), you could skip it and just substitute more vodka. Or just buy a couple of those tiny airplane-sized bottles of brandy at a liquor store: just tell the clerk you want a decent brand for cooking.

When the brand I'd used for years was mysteriously no longer available, I asked several chefs what brandy they used for cooking (you do want something drinkable, but not Cognac). the "winner" by a longshot, was DeVille brandy. You can keep brandy in your cupboard for a VERY long time w/o danger of spoilage, so it's a good choice of liquor to have on hand for cooking -- unlike wine, which -- if you're not going to drink it -- will go bad. I do think once you try it, you'll find many other uses for it in your cooking. I wouldn't omit the brandy from the vodka sauce. I find it adds a roundness to the sauce that is unattainable otherwise.

Hi SMSF - Most Penne alla Vodka recipes I know don't require brandy, including those from fine cooks such as Marcella Hazan. If you choose to make the dish without brandy, it will taste fine.