Metz also make some models that take a sony interface. The newer sony flashes for the alpha series of cameras are also supposed to work (with an adapter available from sony).
Just to make sure the OP doesn't misunderstand... The DSC-R1 and previous Sony models use a totally different flash system compared to the new Sony Alpha DSLR-A100.
The hotshoe design and flash system for the Alpha is based on the Minolta Maxxum system. Basically, the new Sony flashes that are compatible with the Sony Alpha DSLR (HVL-36AM, HVL-56AM, etc.) are rebranded Minolta strobes and will also work with KM DSLR models.
For example, the new Sony HVL-36AM is the same flash as the Minolta 3600HS(D), and the new Sony HVL-56AM is the same flash as the Minolta 5600HS (D). Ditto for the other compatible strobes. They're based on the Minolta strobes and were rebranded by Sony.
These strobes are not compatible with the Sony DSC-R1 (they won't even physically mount as the hotshoe design is different, much less work).
The foot (SCA3302) that Metz offers for their strobes like the Metz 54MZ4 that works with the KM DSLR models and new Sony Alpha DSLR is *not* compatible with the DSC-R1 either. It's designed to work with the Sony DSLR and Minolta DSLR models, not the DSC-R1 (which uses a flash system designed by Sony).