The PU sniper rifle wasn't manufactured until after the Stalingrad battle. In Stalingrad, Zaitsev used a Mosin Nagant 91/30 with a 4X PEM scope not the PU that was shown in Enemy at the Gates. After Stalingrad Zaitsev was issued a Mosin Nagant 91/30 with a PU 3.5X scope.
I actually should have said the PU wasn't made until late in the Stalingrad battle. The battle took place between 23 August 1942 to 2 February 1943 and the PU went into limited production in 1942. Vassily fought there as a sniper from November 10 and December 17, 1942. Before that he used a standard infantry 91/30 and did pretty damn good with it. He preferred the PE/PEM sniper rifle and if you ever shot one you'd see why as it's more like a modern scope. I've restored an ex-PEM using a repro scope/mount. BTW, 1942 PU rifles are more rare and highly sought after by collectors.
I just ordered mine from classic arms. I paid $20 more for a Tula but thats ok they do have tula and izhvesks in stock. http://www.classicfirearms.com/c-r-eligible
