Hi there,
First, thank you for your interest in continuing to support us, it truly means a lot to us.
Currently our only “upgrade” option for purchases made on our webstore functions as follows:
Purchase the Supporter Pack you would like to have at full price and send us a support ticket (just like this one) letting us know you have purchased the upgrade. Once we have confirmed the purchase, we will refund the original purchase back to you. This process will not effect any data or progress you may have already made and you will be free to continue playing immediately.
Unfortunately, this process does not work for players who have purchased the game through Steam as we do not have the capability to refund a Steam purchase.
Thank you again,
-Wick