I have a Pursuit alarm system in my '95 that comes with a remote keyless system. I run around most of the time in the valet mode, though, because when the alarm is on the lock/unlock noise is so f-ing annoying. I know Pursuit systems are still around, and there are plenty of other good ones too. It might not be that much more just to get an alarm that comes with remote.
I will never own a vehicle without keyless remote ever again. I had to replace the remote once and I was using the key for about three weeks. Never again.