I know they're about 2.5 - 3 mm but does anyone have a list of buds that size?

I'm new to high quality headphones but I've found a few pairs that are in my price range and that I like. But I'd just like to know what you all think.   I want something balanced and portable. and around $300 or less   What's your opinion on them?  Could you recommend anything...

I want a good pair of balanced headphones preferably in-ear or over-ear that have good noise cancelling and little to no leakage as I plan to use them on the train and in crowded areas. I don't care too much about their size as long as they are portable, but I'd prefer if they're small. I'd...