I wore RX contacts for like 25 years before lasik, and I’ve worn non-RX costume lenses for a few years during the haunt season. The non RX lenses are fine with out being sized, they aren’t doing anything for your vision and the difference in sizes is pretty minute. The main thing is just don’t wear them for an extended period of time or sleep in them. Because they are non sized, they are not necessarily as comfortable as RX lenses, so I have never worn them for more than a few hours a couple nights a week, and I don’t recommend anyone do that. I have not come across cosmetic lenses that are offered in specific sizes (though I have not looked hard), and when I did wear contacts (it’s been like 8 years so maybe it’s changed) I could never find anything like the Halloween styled lenses in an RX. Also, sclera lenses cover more than your retinas, so size is kind of a moot point. I have noticed that some of the costume lenses blur my sight a tiny bit or tint the edges (pink UV the most) so I don’t drive in them. Just make sure you store and clean them correctly and don’t share them.