i made the same mistake a while ago, its better to subscribe on their website and u get access to everything during your sub. maybe if you email them they might help u out since this set came out about a week before it went on itch
Viewing post in Enemies Pixel Art Asset Pack comments
Hello, when you buy a bundle on itch, you only get those bundles that are available at the time of purchase. Unfortunately, we cannot set it up differently on the itch.
You can write to our support team : https://craftpix.net/support/
For those who bought the itch bundle, we give a free subscription for a week.