What would be the correct scope for the side rail on a Romanian AK-47?, and what would be the correct red dot?....

the Russian POSP series for the side rail, and probably the Kobra Red Dot series of scopes if you want that kind of optic.  

I would guess the correct optic would be a Romanian POSP 4x24 which mounts on the siderail.
But the POSP scopes are havy and bulky, you might wanto check out the red dots out there for AK's. Kobra, PK-AS, etc...

I've got a POSP 4x24? and on another I went with a low profile over the centerline Russian weaver rail scope mount with a smaller type Russian 4x scope that is like the POSP but without the attached mount.  More compact, but I don't see them available anymore.  I need the magnification due to vision changes in the last two years.  Old age.  These seem to be really nice scopes but they aren't low weight.