What's a good substitute for Shiner Bock? Shiner's hard to find outside of Texas

You want a rich beer with substantial body. I believe bock beers are lightly hopped, so you don't want a bitter beer. Try finding a local bock beer from your local microbrewery, although that might be hard because bocks are seasonal. Or perhaps you can find a Sam Adams Bock--that might be heavier than the Shiner, but I think it would still be good. If you can't find a bock, then ask for assistance at the liquor store. They are very helpful in guiding customers to good alternatives. I definitely wouldn't use Budweiser, which I think is totally undrinkable and would give the dish an off-taste. (And I come from St. Louis, so it takes a bit of nerve to say that.)

My experience with chile and beer,is that dark beer can leave bitter notes with long cooking and a lighter beer holds up better. I just use Dos Equis or Budwieser. They both taste great in chile for Frito Pie.

Any dark lager would work just as well in the recipe!