You can purchase it here on Itch.io by pressing Download Now and then "Pay with Paypal". If you do this you'll have permanent access to the Premium Version.
If you sign up on SubscribeStar you can also have access to the Premium Version for as long as you pay for the monthly subscription (the lowest subscription tier is 3$)
Patreon also works like SubscribeStar but we put up a censored version on there (there's a way to remove the censorship but you'd have to buy the subscription and join our discord to find out how)
Hope this helped clearing things up!