In my house I have two external outlets like this:
Both of them cracked and need replacement. Though I found a straight replacement (Leviton 4986-GY 1-Gang Duplex Device Wallplate Cover, Oversize, Weather-Resistant, Thermoplastic, Device Mount, Horizontal, Gray) based on reviews they will crack soon again.
I tried to find alternatives but there are no clear candidates. Ideally I'd like to install something like weatherproof deep in-use cover one but they don't cover underlying round box. What are my options?
Update. Followed the answer, worked like a charm! Need to paint around outlet.
Best Answer
Easy. Just get a round to single gang adapter like this:
Amazon even suggests this is bought together with an in-use cover and GFCI, so you are clearly not the only one with this problem.
If you don't have GFCI on this circuit, you should add it. Even with an in-use cover, that would be better done inside (breaker panel or an earlier receptacle in the circuit).