If you are able to immerse while on your trip, that is preferable to delaying immersion until after your return. You can find information on locating a mikveh under Mikveh Directories on this site. Be sure to call ahead to check about hours, price, and what supplies are available.
If, for whatever reason, you are unable to immerse until your return, you could try to contact your local mikveh ahead of time to arrange for a late-night immersion. Such arrangements are often possible for an extra fee.