current draw of a relay?

A standard Bosch/Tyco relay has a 75 ohm coil which means it pulls 160Milliamps.  Way too much for your Gps device to power.  You can still power the relay with a transistor.  I have no idea what sources you have there to get a transistor.  I can give you an NTE part number if there is a supplier there.   An NTE 331  or a 2n6488   or a TIP3055 will all do what you need.  Let me know if you can get either of these and I will draw you a diagram.

RadioShack (A stateside electronics retailer) does sell a relay with a 400 ohm coil, this will have a 30 Milliamp draw.  Maybe you can find something there.