I know of no such service on the Central Coast. You might try calling your local nursery to see if they rent plants. There are also organizations that rent live plants for special occasions (weddings, banquets, conventions). Try the yellow pages or call your local chamber of commerce.
I would like to add that you should not feel bad about buying and enjoying a live Christmas tree. Christmas trees are a crop just like broccoli, strawberries or apples. The trees are planted for the purpose of producing Christmas trees. They are grown to a certain age and height and then harvested. If you do not buy a tree, that tree will not remain in a forest and grow to be a big tree. If the tree cannot be sold, the grower will eventually cut it down, clear the ground, and plant a new crop of trees.
Some Christmas trees are cut out of natural forest areas. The removal of these young trees is also necessary. When trees reproduce under natural conditions, they often emerge en masse. If these stands are not thinned, few to none of the trees grow to be strong trees, therefore, the stands are thinned. The best trees are left, some are Christmas trees, and the rest of the thinned stock is left to decay and return to the soil. So, please do not think you are saving a tree by not enjoying a live, cut tree in your home for Christmas.