There are kits from Jaycar etc for remote unlocking (or including an alarm) - since the car didn't come fitted with it. There should be a module (typically under the dashboard or in the engine bay) with a non-genuine look to it. Is it getting power, or is an in-line fuse blown ?
You can probably get a locksmith to cut new keys and clone or transplant the transponder chip - I had an automotive electrician clone the 2007 XC90 transponder into a spare key blank...not cheap but factory fresh. Otherwise it's less hassle as you say to tape the chip near the antenna loop and use an old-school key.
(I use the service key on the XC90 - much more durable and less bulky than the remote keys)
