1989 Cougar Front License Plate Screws

Hi. I own a 1989 Cougar that has no front license plate. I need to
install a front license plate for my state. I can't seem to find the
right license plate frame or screws for this. There are two little
holes in the front bumper. I have found license plate frames at local
auto stores but they all say, "mount this with the original screws".
I don't have the original screws. I am afraid to use any other screws
because it may damage or crack the bumper plastic. The screw holes
have no thread. What's the best way to mount license plates on this
vehicle?

Any suggestion would be greatly appreciated. Thanks.