Where to get a thermal scope in socom us navy seals

You must purchase it in the Armory. Go to the scope attachments and purchase it. But if you can't purchase it, it must be your LI Rating. You must have a good rate to apply that scope. To do that, just complete lots of missions, complete lots of bonus and secondary objectives in missions to get a higher LI Rating. Doing knife kills, restraining hostile and hostages can also help.