^ I agree, i could use a tunnel too.
Mikey i DO have a suggestion, although it is not an actual tunnel it would be like one

and you can fix the height you want it at !
But what i am thinking is using a tarp?
Just some how get something to hold up a tent like area, or just keep it suspended abit so that the dog can go under and through, and somehow pin it to the ground.
It would work
Im not the best at explaining, let me have another go lol
A blue tarp, and than pin the corners to the ground, but underneath it have something to keep it up in the middle like a tent !
that way the dog can go under it and run through, like a tunnel.