Hi Tyson

Unfortunately the only ways are:
1. installing the original key and antenna
2. using AndroidX's dummy key
3. if you don't do 1 or 2, you can simply enter the user code each and every time you turn the ignition on
4. ask nicely, send your dash to italy and (if you can get them to do it) get Aprilia to remove the immobiliser
5. buy a special 'no imo' dash from Aprilia Racing

I did #3 for a while, but it eventually drove me nuts so I ordered a dummy key.

#1 is cheap and easy. Just wire a toggle switch into the main ignition line to the barrel, then leave the key in the 'on' position, wrap the whole lot up in electrical tape and tuck it behind the dash. Job done! No cost, except the switch.