You could have brake bosses brazed onto an 80s vintage road frame. I'm going this route with an older Tange frame, has clearance for 38 in the rear, and 40 in the front. When it's finished, I'll post it.
i have been searching ebay.. there are some Alan's on their now that i would love to get but too large for me.. I like the look of the Alan's or the Vitus.. that Sean kelly look.. I would actually like to see a pre'80's one for sale.. they seem rather rare.. I have yet see one.. been looking for quite awhile..
The add your bosses thing is not a bad idea.. I have rig like that currently ride as the grocery getter.. I believe it was a 70's Motobecane Grand Jubilee that somebody welded all kinds bosses actually.. kind of interesting.. I chromed it and set it up as a porteur style bike..