You can get Up-armoured T-34s as part of any of your Mixed Tankovy Batalon Medium Tankovy Companies.

Just use the rules from a T-34 obr 1941 and use them in conjunction with the Extra Armour special rule on page 144 of Ostfront.

Extra armour gives a T-34 a Front armour rating of 7 and a Side armour rating of 6.