Any of the shields need the “While Terrified, gain ammo regeneration” anointment.
The shields I am ideally looking for are a: Transformer, Stop Gap, or Re-Charger. However, if you have any other legendary shield with that anointment, let me know as I may still be interested.
The grenade can be any type/rarity of grenade with the “On action skill end, apply Terror to yourself every 5 seconds”
Let me know what you have and let me see if I can help you out, although I will preface that I have very little M4 specific drops.