Obviously finding a neighbor, fellow hobbiest, or friend is the easiest and cheapest but may not give you the results that you are expecting.
Many of the fish stores in the area also have maintenance services. I'm not sure if they offer a vacation only package for service but I'm sure a few do.
I have my tanks on a controller that is accessible while I am traveling so that I can not only monitor my tanks parameters but I can feed my tank while I'm not there. It took years to get all of the pieces that I have connected to my controller but I honestly couldn't have a reef without my controller to help.