I have a window unit that is currently in a opening in the wall. I will be moving the unit to a window and need to get the side fitting that goes on both sides of the unit (i.e., since the unit is thinner than the window.) I went to Home Depot, and I was told that this is only sold with the unit itself. I suppose I should try Lowe's, but certainly, I should be able to by it online, which is good enough for me. Any ideas?