Where do you cash in a 1957 A 1 dollar bill that's not a silver certificate?

Answer 1

This isn't a valid question for two reasons.

First, ALL 1957-series US $1 bills were printed as silver certificates

Second, "cashing in" a bill means taking it to a bank. Banks don't buy old currency, they're only allowed to exchange it at face value so you'd only get $1 for it.

However you wouldn't lose very much because 1957-series silver certificates are very common among collectors. In average condition they retail for less than $2.