I'd have to agree with those options. You can't get away with not having to modify a pattern if you want it to be accurate. Honestly no matter what you do you will most likely have to make your own pattern for the collar, you could find something close and just change the size to be what you need to get the desired look.
I know there are plenty of double breasted patterns from the usual brands. Just flip through the books at you fabric/craft stores and see what comes close. I would look for the pattern meeting two of the conditions you're looking for. It of course needs to be double breasted, so I would go with that and the collar because adding length is quite easy.
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