Ordering iphone 5s

Hey guys so im ordering an iphone 5s and im running into an issue . You see, im currently on verizon's service and want to change over to tmobile. I'm no longer under contract so thats not an issue. my issue is that the only tt mobile store near my house, doesn't have any iphone 5s's in stock. Also because of the way tmobile works, i can't order one from apple otherwise i have to pay the full price right then and there.

This leaves me with only 2 options that i can think of, and i need your help to tell me if the first one will work.

I can order the phone from t-mobile online, as they have the silver one in 16gb (which is what i want), and it would ship immediately. My problem with this is, i want to port my number over to tmobile. If i port my number over, and have to wait a few days for the phone to arrive, will i be without a phone for a few days? Or will my number stay on my verizon phone until i turn the iphone on and activate it.

My only other option is to wait until tmobile gets it in stock

Please help guys.