Ride-on car for 4 year-old boy (Clarkson)

Our little guy is currently fixated on having a "real police car" so that he can catch the badguys (squirrels, I guess!), and has somewhat fixated on the ride-on toys with the little motors that kids can drive around. Should you have one that is collecting dust, or that you have written off but that might be fixable for a tinkerer, I would be very grateful to give it my best mechanical shot for our little policeman. :)