You're out of luck, I'm afraid. Neither of the brakes have as shallow a drop as 47mm. I had thought the Monitor one might manage it, as it's the shallowest 40s/50s brake I've come across, but it wasn't to be. TBH the drop is one I believe to be common for modern bikes, and I'd have thought that really vintage ones (like yours) that were designed for shallow drop brakes would still have a larger drop fork design that what the modern forks have. Perhaps due to the (possibly wrong) idea I have that even purist racing bikes back then had wider/fatter tyres, seeing as this seems to be necessitated due to the tyres not being designed to be pumped up to 100+psi tyre pressures, so the tyres were bigger to compensate for this (ie they'd prevent punctures seeing as running too skinny a tyre not pumped up hard enough increases the chances of 'snake bite' punctures). Anyway, as you say, the deeper drop brakes were pretty ubiquitous back then, but if bikes like yours weren't a rare design then there should still be quite a few brakes around that are shallow enough to be compatible with them. But I'm not sure I'll have any. From memory, the Grip-It brakes I have are very similar to the Follis brake above, so I suspect the drop would also be similar, which is unfortunately deeper than the Monitor that is significantly deeper than the 47mm you need. But I can still look for them if you feel there's a chance of success.
the brake caliper seems to be the first part that became alloy, pre-war even. 
