Some of my turkeys were using the same nest boxes as the hens, although they had to let their tails hang outside the box. Others laid directly on the ground.
The solution I came up with was a large wooden crate, about the size of a laundry basket, open side up. A solid plastic laundry basket would work too, as long as you put something heavy in the bottom to keep it from turning over when they climb in.
I used a large plastic dog house for my turkeys, or you could use a large dog crate with the door removed. Just fill it with hay or sawdust/shavings as a bedding and let them have it
Mine loved their nest haven. The great thing is if the nest box is covered it ca be located outside and won't get wet inside if it rains.
If anyone is interested we manufacture plastics turkey nestboxes, one 8ft unit comprises off 5 nesboxes. As used by Aviagen Turket Ltd, Formally BUT. Also we have just started manufacture of a chicken nest box, each unit had 4 nestboxes. web site www.goodwinplastics.co.uk