Cave Story's aspect ratio doesn't fit my monitors

The game is 4:3 but the only monitors I have are 16:9 and 5:4, so the game will either be stretched or leaving awkward open space. Is there any way to correctly scale this game on 4:3 monitors?, because Google turns up nothing.

 

You can try this, if you want, you can toggle it to make Cave Story widescreen most of the time (some rooms are too small to fit in the ratio, so be expecting 4:3 with black bars).

 

or just play in windowed

 

You can try this, if you want, you can toggle it to make Cave Story widescreen most of the time (some rooms are too small to fit in the ratio, so be expecting 4:3 with black bars).

That sounds perfect, I'll have no problem with occasional black borders. I'll try it when I get home, thank you.