https://www.amazon.com/ThunderFit-Silicone-Rings-Men-Breathable/dp/B088845H7C its the 9.5-10 size.
Different rings from different outlets may have different sizes available. Do you know what kind of ring you want, i.e. what material/design? I got a plain silicone one, it comes in sizes up through 16: https://www.amazon.com/ThunderFit-Silicone-Rings-Men-Breathable/dp/B088845H7C (~$7)
Upsides to silicone: easy to fit nicely even if your knuckle is significantly larger than your inner finger, very easy to take off in case of emergency, extremely cheap, scratches don't change the color. I'd argue it's a great first ring for testing things out before committing to anything.
If you're not sure what size you are, go to any jeweler and ask them to size your finger for you, it takes a minute of their time and they're probably sitting there bored anyways.