Where can a Reservist 12N E4 promotable find a unit needing volunteers for upcoming deployment?

Unfortunately it doesn’t work quite that easy. Your best bet is to maybe get ahold of a patch chart and seeing who may be deploying in the near future and calling branch to see if you are able to PCS. Again, sounds good on paper, easier said than done.

Not sure if you found your answer I see this is an older post but I know Drum has an upcoming deployment

If you really want to deploy then ask to be transfered to the Regimental Engineer Squadron in 3D CR, Fort Hood TX. We deploy every other year. I just got back from a deployment and literally am training for another one next year. 12 or less months on 12 months off. You will deploy with this unit guaranteed. They need 12N E5's too.