You can get 3mm flat top led's and black bezels for them from
Lighthouse
The
Bezel is small enough to look good on the bumpers, and at 7 cents each not a bad price, they have the 5mm ones also.
If you use the Tamiya lens paint, clear orange or clear red to dip the leds in does not degrade their brightness and yet looks like red or orange lights.
JimN