You have to get the key from a dealership. You have to show proof of ownership (drivers license and pink slip?). Call them and make sure what paperwork you need for the key before going in. Key is about $50. It will come ready to work with the bike.
Alarm fob you just need to buy. I believe you can get it to work with your bike without them using the shop computer. Check your alarm owners/users manual. You will need all fobs at once and the one you have lost will no longer work. If you find it you can "hook it up" along with the others but you need them all at the same time.
If you are concerned about the lost key being used to steal you bike you can have it "deleted" from the bike's ECU. The dealership will have to do that and you will need any keys that you want to work with the bike at that time as well (including the plastic wallet key).
If you find it you can have it reatached to the bike but the dealership will again have to perform it and will need all the keys you want to work with it.