In the past MAC group in the USA handled Mamiya parts and service and they were great to work with, and could easily supply that part. Mamiya recently pulled service back in house for this sort of thing so I think MAC group is not able to supply mamiya parts and service any more, sadly.
Ed
It's not just service. MAC no longer has anything to do with Mamiya.
MAC Group [Mamiya America Corporation] had sole rights to the Mamiya name and distribution of Mamiya-branded products in the U.S. for a very long time. Those exclusive rights have now expired and have reverted back to the parent company.
This could possibly be a good thing for U.S. consumers as MAC just about killed the brand here by pricing everything so high that very few could [or chose to] afford MAC-imported Mamiya products.
Every U.S.-based photographer I know who has purchased a new Mamiya product in the last ~10-years [an admittedly small and anecdotal dataset] did so when they were in Europe or Asia. The savings [even after taxes, currency conversion, and duties] usually more than paid for the entire trip.
MAC would also choose to not import certain Mamiya products they felt might compete with their own marketing strategies,
e.g. not importing the ZD because they were marketing 645s with Leaf backs [this being before Leaf and Mamiya merged].
It will be interesting to see how quickly Mamiya-Leaf reestablishes distribution in the U.S. For example, if you check the B&H website you will see that they only list the remaining Mamiya products they have in stock. Any current Mamiya product that B&H chose not to stock but to have drop-shipped from the distributor - such as the Mamiya 7 lenses - are no longer listed at all.
It will also be interesting to see if there will be a new pricing structure to go along with any new distribution.