I don't understand why you drilled the cylinder out. You just take the steering column covers off and there's bolts or something to release it, or dash panel if in the dash.
If you do that next time at a junkyard you should be able to extract a replacement for that broken piece too.
If you get a new cylinder already keyed, and a matching key, it will need programmed and since you don't have two already working keys, will need to use a capable scan tool, or have a shop or locksmith do it. Plus, your new key will not be able to operate any of the door or hatch locks so it isn't the route I would take. I suppose you could rekey (or take from the donor junkyard vehicle) all of the cylinders to the new key.
Even if you plan to use a keyfob or door buttons to lock and unlock doors are cargo hatch because there's no key, it becomes more problematic if the battery drains for some reason, then only a manual key in the cylinder will work, or other various burdens like jumping from the starter cable or popping hood and doing so.
A dealership shop can look up your key code from the vehicle VIN and cut a key that matches existing locks. A locksmith can (though I expect it's more work than keying the other direction from key to cylinder pin matchup) determine what cut a key needs, based on your existing lock cylinders for the doors, so one key will do everything, then key the ignition cylinder to that cut key. That key will also need programmed, anything but the original key will need programmed and originally, it was programmed in too!
You're better off getting at least 2-3 keys made so from then on you can use those two to program in new keys yourself via the method in the owners manual... that is, unless Ford changed the method, not 100% sure about 4th generation Explorers.
