I went to two of my local dealers to buy replacement engine and cabin filters and neither stocks them.

What's the best place to order OEM parts?

 

...your dealer can't get these items in, within a couple of days?

 

Go on Ebay. The Mercedes R170 parts fit in the Crossfire. Search under Mercedes Air Filters or Mercedes Cabin Air Filters. You might want to call up a Mercedes Dealer first to get the correct part numbers, so you don't buy the wrong version.