Shock Trooper armour schematics are purchased from an Imperial recruiter by a Master Trader (Munitions). The trader then crafts the armor and can sell it to anyone. You must be aligned with the Empire, and of Combatant or Special Forces status to equip the armor. However, if you are on leave you can still wear the armor, but if you take it off you have to be on duty to re-equip it.
The quality of the armour is totally dependent on the core that it was made with. The trader simply uses the Shock Trooper appearance instead of a regular appearance. Shock Trooper armor is a type of assault armour.For more details check the Imperial faction items.