I carefully removed the best ones I had from multiple grille halves and used them over. However, I just did a little searching on my favorite industrial supply house's site, McMaster-Carr (mcmaster.com). Based on the numbers you gave (and guessing that the hole the bumper goes in would be 1/4"?), how about part number 9309K15? $9.50 for a pack of 100, $.095 each! If they are right, buy a pack and sell to all your cougar friends! Hope this helps.
Regards,
Bob