Where can i get a 7 spline lug nut key?

You can try going to a tire shop and having them remove the lug. They usually have a bunch of different keys so they can unlock any wheel. After they remove it put on your own lug. If you cannot find a key that fits and you need to remove it there are a couple of ways to get them off. You can actually break the wheel studs, this can be done with a bar and a big hammer. Place the bar on the lug and swing away. The problem is they you have to replace the studs. Another method is to plug weld a nut to the lug and then you can unbolt them.