I’m not sure what the Lowes ones look like, but back in the day when there used to be new construction, I used a ton of the Lambro 4" under eaves vent caps. They are basically just a modified dryer vent cap and use the standard 4-1/2" hole. Sometimes if the eaves is a little too narrow, I'll pad it with a small block of 1X that I prime with BIN before I mount it, so it matches the white vent cap. I think Arlington also now makes blank plastic mounting blocks that can be used instead of 1X wood for this.
Lambro I just happened to have this type on hand and the room for it, so I used one for the second floor bath on my own house. Same 4-1/2" hole, but a slightly larger footprint than the Lambro in the link above.
Deflecto