While the majority of 7.62 optics are for 7.62x54R and the SVD Dragunov, there is one version of the BelOMO POSP that is designed for use with 7.62x39 and has an appropriate AK mount - The POSP 4x24V.

This is commonly called 4x24 Simonov due to the reticule pattern which is intended for civilian Saiga's and usually has the standard AK MTK83 clamping mechanism instead of the SVD mount.

What makes these excellent optics is the quality to price ratio and the fact that the chevrons are calibrated for 7.62x39. Read more HERE

For a great reference on classic 7.62x54R optics, visit dragunov.net. Herr Berg

Also courtesy of Dragunov.net here are the zeroing instructions for any PSO or POSP type optic

***
1: Looking through the scope, align the top chevron (inverted V) with the center of your target.
2: Fire a few shots to determine if your point of aim equals your point of impact (POA = POI).
3: Holding the rifle steady aiming at your target, turn the scope turrets to move the reticle over to your POI holes on the target. You may need to repeat this process several times.
4: To avoid “chasing your zero” take at least three shots between each adjustment of your scope's reticle.
5: Once you have determined your POI = POA you can now adjust the numbered part of the two
adjustment drums on your scope. This is called slipping the scales. If the numbers on the turrets do not reflect "1" as your elevation (top drum) and "0" as your windage:

1: LOOSEN (do not remove!) the two silver screws on the top of each turret enough to rotate the numbered part of the drum. Ignore the tiny center screw
2: Spin the center numbered part of the drums to reflect zero (0) for windage and one (1) for elevation lined up with the black line on each index plate.
3: Re-tighten the screws (hold the top of each drum secure as you do this or it will rotate as you tighten each screw).
4: Take a few more shots to verify all is correct. POA should now = POI

***

Kalinka Optics PSO and POSP manual here.

For non PSO type optics the choices are much more limited, however there are some versions of the PO4x24P2, Kashtan and PO 3.5x21P that are calibrated for 7.62x39. These are very rare but do exist

PO 3.5x21P Venezuela is a dedicated x39 optic and while heavy has amazing clarity and great FOV

Please note there are airsoft fakes of PSO and POSP made in China.

Most commonly you will see them for sale at very low price points. They will often be marked 4x26 but no real version of the PSO or POSP is 4x26, they are 4x24. Key points are the occular assembly, the types of main screws and set screws used, the on/off switch and the illumination bulb. 

There is also recently an airsoft or faked copy of the PSO 3-9x24

At the time of this update (Novmeber 2016) I have not seen or heard of any other fakes except one version of the Kobra.