again, ebay.
You'll want a kit with a remote input (to be honest don't even worry about that it seems t be standard on even the cheapest nastiest sets available).
You'll want 1x master (or 2 if you want the passenger lock to activate all the locks as the drivers would)
1x secondary (or not if you get 2x masters).
You could also get a solenoid to pop the boot. I'd strongly advise against it though (assuming you blank off the boot and remove the handle) as it's handy having the ability to open the boot with a key still. Dead battery, fucked locks, etc. BEen through it myself and it's much easier to use the boot, unless you're handy with some tools to "break in" without damaging stuff, that soon wears thin though.