The 389/241 and 689/241 were used on '66 Norton Atlas and Matchless G15P models. The 241 suffix was Amal's stocking number to indicate the carburetor had been configured for that particular model (jets, slide cutaway, etc.)
To my knowledge, the "handed" pair, 389 and 689, was only used on a very few models. Nortons in '66, BSAs in '66 and 67, and some hybrid Matchless. And, last I checked, there were no newly manufactured 689s. I'm also pretty sure the newly manufactured 389s don't have the old stocking numbers stamped on them.
Your best option might be to find the best used pair possible, and have them straightened and resleeved. If you need them stamped with the correct numbers, like for a 100 point restoration, you could file the old numbers off and restamp them. Since it's not a VIN, it's not illegal.
The following numbers are 1 1/8" carburetor sets, Norton: 389/241 689/241, 389/236 689/236, 389/237 689/237, 389/242 689/242. BSA: 389/200 689/227, 389/230 689/230. Matchless: 389/237 689/237, 389/241 689/241, 389/242 689/242.
BSA carburetor sets 389/228 689/228 and 389/229 689/229 are 1 5/32" carburetors. Triumph never used a "handed" set from the factory.
Of course if it's not a restoration, you can use 2 389 monoblocks provided the room for them is not an issue (some Nortons) or you can use concentrics if it is. Both are available new, and configured how you need them.
Here's a BSA pair, with some float bowl extansions: