Is there any way to get a refund for clothing items that you accidentally click on in Pokemon Go?
In order to have Pokecoins potentially refunded, you need to submit a ticket to Niantic. In the ticket window, there is an option for "Items & Currency" as the issue type. Previously, there was an option that allowed you to indicate you purchased the wrong item, so hopefully you can achieve the same results by filling out the description field.
There are users on reddit who have encountered similar situations. However, there are mixed reports stating that Niantic did refund their Pokecoins whereas others are stating their Pokecoins were not refunded. Regardless, your best bet is to submit a ticket and see what Niantic does.