Mine is from an old Valliant I believe. Which look fairly similar to the Jeep one, which isn't much of a surprise to me because the local Chrysler brand here in Oz in the 60's & 70's was Valliant. lol
Or, you could use LED string lights (white) and make a little recess in the license plate area you made. Cheap, easy, and very bright.
Walmart, Kmart, and most auto stores sell them. LED's last a very long time. No bulbs to replace.