Easiest, fastest method - (for me) no putty required.
Trace the oval shapes onto a piece of .040 styrene. Don’t have any? Go to Ace and get a for sale sign, or use an old gift card.
Cut them out, insert into openings so that they are flush from the outside, not the inside.
Spread CA around the edge, hit with accelerator. Sand with sanding block. Done.
I do this on a regular basis. Less than ten minutes start to finish.