EXP Weapon Mini isn't in the Rising Weapon Badge 4 shop.
It might be added with Episode 6, or the next maint. I know we didn't have EXP Weapon Minis in the Photon Drop store until recently.
I hope so. I've been stocking up hard on badges for my Atlas needs but I never got on the huge AQ grind train early on in the game so I don't have a million Photon Boosters for EXP Weapon Minis. I got a lot of stuff to +35 here!
You can solo AQs pretty easily at 80+. You don't need to increase the threat to max to farm boosters. Since they drop no matter what.
@MisterJaySnek You can also exchange astracite for photon boosters and you may have a lot stockpiled from running Tokyo Keys