@Kbuckley Thanks for reaching out!
I'm sorry to hear that you've lost your rainfly! Unfortunately we do not sell that piece separately from any of our tents. In a pinch you could probably rig up a tarp system to keep the tent dry, however that would require some careful measuring and staking of the tarp. Lastly, it is a very long shot but if you're in one of our local REI stores and attending one of our member only garage sales keep an eye out for a Kingdom 4 tent, you may get lucky and find one that has a damaged pole or tent body!
I hope this helps, good luck!