Hello Peter,
I think that it will be
very difficult to refill your Campingaz 907 butane canister in the United States. However the smaller Campingaz disposable "Valve Cartridges" like the
CV-470 Plus are available in camping supply stores across the whole country.
I think that you should be able to purchase an adapter in Germany
like this one so that you can use the small Campingaz canisters.
There are two
REI Stores very close to
Baltimore that should have canisters of Butane.
Note that the adapter shown in your picture is called a "POL" and it is commonly used for filling
Propane cylinders in the US (sometimes we have a propane/butane mixture), but we do not use it for only butane.
Cheers,
-Mark