Have you tried it again today? I just tried entering those parts for your car and they both worked OK into the cart - $13.97 for the mount, $15.50 for the primer pump.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E