Are road-bike suspension forks still manufactured, if so, where? For a few years, road bike suspension forks were used at Paris-Roubaix, but now they seem to have disappeared. Are they still being manufactured? If not, why (aside from UCI regulation) did they not persist, e.g. for cyclocross or city riding?
The Rockshox at Paris Roubaix were a Greg LeMond thing. Whatever Greg competed in a few 'out there' cycling innovations came along with him. Remember those tri-bars that gave him the aero tuck position to beat Laurent Fignon in the Tour de France? On that event he also had his own road bars that had an extra position, where the drop handlebar end plugs would be, his bars turned in 90 degrees to give an extra lower position. Anyway, it was his Team-Z that introduced the Rockshox on Roubaix. Seems that your well chosen pic duly notes his special handlebars, the Rockshox and 'Team Z'.

Greg's bars and forks were not widely adopted although his time-trial bars most certainly were. In any evolutionary process some mutations just don't work. As for the forks, the problems with them were that they were heavy, the brake touched the rim and they introduced 'sloppiness' in the front end. Imaginably these problems would be overcome but they were not. I don't think UCI regulations had anything to do with it, the product at that time was just not that good. MTB forks were a bit dubious too back then, only when the disk brake came along did the 'brake rub' problem get properly solved.

There are plenty of 700c forks on hybrid bikes from mainstream manufacturers, generally of the low-end 'Suntour' variety with a spring that does the work instead of any sophisticated oil/air arrangement.

You might want to go to a bike shop and do your own compare and contrast of the bikes with 700c suspension forks. The travel is around 50mm or so and there generally is no adjustment on them. I think Trek do a few models with them, Giant did too on the more expensive 'Expression' models. Although experiences are subjective, I found that along gravel trails the hybrid with no suspension felt better than the efforts with suspension. I wondered if the suspension was doing anything at all, it did not float over the bumps like a full-suspension mountain bike does and there was no real cut in handlebar vibration.

Here is a Suntour offering with coil spring, preload adjuster and lockout. This model is typically found on things like deluxe Trek hybrid bikes:



The brakes are V-brake, the hole in the top of the brace is for mounting a reflector and you cannot put a nice set of road brakes on there. Other versions of this low end fork exist for roller cam brakes, which you obviously do not want!!!

There are some more desirable models made by Suntour for cyclo-cross and the hybrid market with 'proper' air adjustment and rebound, maybe even remote lockout. I am not sure if these models are OEM only or if you will be able to get hold of them locally:



As for Cyclo Cross, checkout the Suntour NRX models, with disk and all the sophistication you could wish for in 700c:



http://www.srsuntour-cycling.com/dstore/products/Forks/2845/NRX/SF11-NRX+S+ELD+700C+LTD.html

That fork should give you the ultimate in comfort for the front end of your road bike. Although for cyclo-cross it has the makings of a very tidy commuting machine...