GPS Antenna Selector: How to electronically select one antenna from multiple available antennas?
I believe the component you are looking for is called an RF switch. They are used for example for switching the TX path of bluetooth and wifi chips to a single antenna. RF switches are quite inexpensive (relative term, I know), and come for many purposes.

The terminology for RF switch classifications is similar to regular switches, i.e. SPDT means single-pole-dual-throw, i.e. a single common signal can be routed to two locations.

Here's a relatively generic one which works over a relatively large frequency band (incl. GPS)
http://fi.mouser.com/ProductDetail/Skyworks-Solutions-Inc/SKY13270-92LF/?qs=sGAEpiMZZMtsfndvJ9ArQ1GAoWUJ3yIM3lKzNTG0W6Y%3d

Datasheet: http://www.mouser.com/ds/2/472/200128G-23362.pdf

Please note that RF switches are nowadays often minuscule components and can be difficult to solder manually for the unexperienced.

Here's a more generic article about RF switches by digikey: http://www.digikey.com/en/articles/techzone/2012/aug/rf-switches-simplify-multi-antenna-systems