Having a hard time finding them

Spheres can be got trading in 10* weapons and Units, those along with normal grinders you will find yourself rolling in just playing the game more at higher levels

If it's lambda grinders you need just keep doing Falz for now when ever he shows up

Grinders seem to drop frequently from enemies over lv 50. Especially during urgent quests that involve killing enemies to meet point quotas.

@Bl4h i don't know if it's because it's still in beta. But i can only trade 10 star weapons at the swap shop, it doesn't give me an option for grinders. And i have a TON of them

advanced quests and raise the threat level to 50 you will have more than you know what to do with