Helping my 4 year old..advice please

So my 4 year old son has very bad anxiety. His dad my husband works a night shift job and our son does not like it. Every time he has to work our son will stay up almost all night long complaining, crying, whining, and freaking out about his daddy being gone. I don’t know any Good ways to help him out. I was thinking about getting him a “daddy doll” with his dads picture and voice recording but I don’t know if it will help. Any advice will help! Thank you.