Is it a bad practice to use break in a for loop?

You can find all sorts of professional code with 'break' statements in them. It perfectly make sense to use this whenever necessary. In your case this option is better than creating a separate variable just for the purpose of coming out of the loop.

No, break is the correct solution.

Adding a boolean variable makes the code harder to read and adds a potential source of errors.

Lots of answers here, but I haven't seen this mentioned yet:

Most of the "dangers" associated with using break or continue in a for loop are negated if you write tidy, easily-readable loops. If the body of your loop spans several screen lengths and has multiple nested sub-blocks, yes, you could easily forget that some code won't be executed after the break. If, however, the loop is short and to the point, the purpose of the break statement should be obvious.

If a loop is getting too big, use one or more well-named function calls within the loop instead. The only real reason to avoid doing so is for processing bottlenecks.