It shouldn't really be a surprise if you're into AK's but the Russians have produced a number of newer designs for the AK74 than just the older PSO/POSP series optics that we are familiar with. During the past twenty odd years they  have built a few dedicated 5.45 optics which have modern features and interesting concepts. While NPZ has been making some high tech and interesting optics, BelOMO has seemed to stay a little more traditional with their designs, at least with what we have available in the US. Some of their prototype optics are extremely interesting. Many of the BelOMO concepts seem to be aimed at securing military contracts and because of that there are a few prototype models that have made their way to the USA that are not in serial production. 

Being a 5.45 buff I've picked up a few of the dedicated military style 5.45 optics and figured I'd put out some observations and theories along with some hands on experiences.

There are four main optic types calibrated specifically for the 5.45x39 round:

NPZ

1P78 Kashtan - Russian modern issue for AK74M and RPK74

(Includes 7.62x39 versions as well)

NPZ
1P29 - Soviet copy of British Trilux/SUIT

BelOMO
PO 3.5x21P - 3.5x magnification with extremely wide field of view 
(and other limited quantity types like PO4x24P)

East German
Zeiss ZFK 4x45 - Former DDR cold war scope similar to the PSO-1

I have not personally heard of a PSO or POSP type optic calibrated for 5.45x39, but it shouldn't be difficult to use any of them with a 400m zero as long you realize the turrets and additional chevrons won't compensate for bullet drop.

In a pinch POSP optics will work just fine as long as the proper AK or universal mount is used (SVD mounts do NOT slide on from the front and even though they will fit they will not hold zero unless by pure luck)

Top left: ZFK on SLR105 and PO 3.5x21P on AKSU
Top right: 1P29 on SGL31 and 1P78 on SGL31