I found a clever idea (Or at least I think so) for a game camera mounts
These security camera mounts on Amazon are $9 for a 2 pack.
A few sheet rock screws to mount to trees. I haven't tried yet but I am sure it would not be hard to zip tie to a T-post. They can rotate to about any position and seem to hold the weight of the camera.
Cons: they are plastic not going to last forever. And if a determined cow takes to it, it's going to snap.
But I figured for the money it's worth a try.

Look pretty good to me.

Screw it to a block of wood and use U bolts to clamp to T post.

After a little closer inspection the base is in a cast aluminum. So it may last a little longer than I thought

That will work - plus with the swivel mount, just place it alot higher than a cow could bump into and point it down just a bit. Do you have a link to the product?

Camera mount