Any dry cleaners normally does at least minor alterations.

For something like that it’s normally $6-15 per pants.

For regular customers it’s often super cheap. They use it as a way to keep you coming in. It’s a few minutes of easy work for someone with experience doing alterations and they’ll give you a 3 day window, so they just do it when they’ve got nothing higher priority to do. If you come in off the street you’ll pay a bit more.

You don’t really need a tailor for this. It’s a trivial task.