I would contact fcpeuro.com via phone. They do not have any listings for Crossfire parts but they have beaucoup MB parts. I would search 3.2L radiator or coolant hoses for a 2005 slk320 or c320. If you send them a photo I'm certain they will have the parts you need. I have been doing business with them for a number of years and find they provide excellent service and good pricing. They offer both certified MB and other competive brand parts.
Cheers