If you are looking to replace your current system, have a look at
https://www.viper.com/OPTION 1:
If you are looking to unlock your Celica which has a factory/OEM Toyota alarm installed to it, the dealership should be able to reproduce the alarm signal and key chambers to a brand new Toyota OEM Key.
The keys are normally about $260 - $340 USD, and the labor to get a new set all programmed depends on whatever your current dealership charges.
OPTION 2:
Locate and purchase an exact same type of remote key that you already have (search eBay)
Have a quick read through this page
http://www.celica.talktalk.net/autolockign.htmand this one
http://www.celica.talktalk.net/keyreprog.htm