find a place in the US, how much for shipping and duty?
how close are you to the border, might be worth a trip
for a 2 bbl carb, you can still buy a brand new Holley 2300
All Holley marine carburetors are developed to meet the U.S. Coast Guard's stringent specifications. Each has a special marine carburetor fuel-metering system calibrated specifically for the unique engine loads found on watercraft and J-style vent tubes to direct fuel and fumes back into the...
www.holley.com
brand new....don't waste time with used carbs you find on line, they can be Franken carbs that are pieced together and may not work
alternatively, have you tried to clean your carb? I can rebuild my old Q-Jet 4bbl for like $60 for the very best carb kit you can find.
or, if you don't want to take on that task, find a shop that caters to classic cars, they do this kind of thing all the time
the main thing is the cleaning, of every passageway and jet.