Waterford/Gunnar for one, who actually make the high end Rivendells.
Most really high-end (building bikes to race on) steel framebuilders these days use oversized thicker tubes, carbon forks, sloping top tubes, and threadless stems. Which give the bikes somewhat of a 'modern' look. These bikes, made from expensive metals (853/953 etc) are pretttyyy damn close to carbon/ aluminium preformance wise, and some second rate pro teams even get forced to race on them. They're just really expensive, and frankly, still inferior, and don't even look classic so it's kinda like whats the point, but some i've seen in the flesh, have been very nice indeed but i think the same thing for modern carbon/allum bikes too.
If you want an actual faux-retro steel frame, as in, lugs, and straight top tube, lots and lots of builders still make them. Custom builders will do whatever you want. You could even get many of them, like pic related, off the shelf, stock, new. And it's not even exactly faux-retro, they just never changed the design.
I like the aesthetics of these bikes, i would just not go as far as running a quill stem. The rest is fine.
Put all modern parts on it, and the performance is excellent. Infact even with classic parts the performance is excellent. A well built steel fast road bike is a very fine machine, old or new.
It just costs you (minimium) 1000 for the frame and 1000 to build it up.
Your alternatives are a more modern steel bike with tig welds not lugs and sub-par preformance for slightly less or just putting your retrodouche money where your mouth is and restoring an actual classic bike.