There is no feature that allows you to search for a specific person in Gaia Towns. Gaians resort to telling others what part of the Map they are currently occupying and the Square they are in.
For example: Private Messaging someone that you are in "1 Barton 001000". The number 1 being the Square and the 001000 being the zip code. You can also save a favorite location, so you don't have to search for it every time you enter Towns.