I think Amazon. And I would think, it was the way I installed them, that is the issue. When the warmer weather comes, I will add a sliding side door. That will make it easier for shorter people to reach in.
We added struts to the nest box roof. Here is a picture. I did not read the instructions, so even with two, they barely hold it open. They help, but the roof is still heavy.
I think adding a side door would work better. YMMV. I plan to add a door, maybe a slider to the side. It will be...