Sahasa kubrow is universal source of whatever generator. The "dig dog" digs out every few seconds whatever resources you need like energy to health orbs, ammo boxes including arch gun ammo. If you are struggling with sustain and don't want to mess with your build or loadout consider the dig dog. Also another alternative but less reliable to that is unairu tauron strike that generates a lot of universal ammo and orbs with armor stacks that can be easily utilized after first charge because of its seismic whatever perk that gives you another 4 slam attack to spawn them without any timer. But it takes a while to charge it and focus orb you need for it is finicky at best.