Engineers working on the Crossfire project/car at Chrysler have stated the air bag controls on the Crossfire are different than the SLK models because of weight and crash test parameters. However, if you have the old part it will have a part number on it. If it is a Mercedes number then it should interchange OK, but if the number starts with 193 it is a Crossfire specific item and should only be replaced with another exactly alike.
You should be able to find replacements on ebay. Also be ware there may be differences in roadster/ coupe and SRT6 so be certain the numbers match. The later year models 07 and 08 are also different.