Some other options are the Gravity Forms plugin, which can be used to create a custom product page by using drag and drop fields. Very easy, no coding knowledge needed. The nice thing is that Gravity Forms can of course be used for all kinds of other things as well. This asssumes you already have Gravity Forrms, otherwise you will need to also buy the Gravity Forms plugin seperately. But I think it’s worth it because of the versatility. In my case, I want to enable people to enter seperate donation amounts for various sub-categories on one page, entering their own amount, not a pre-set value.
Take a look at https://www.woothemes.com/products/gravity-forms-add-ons/ for the extension and https://lucasstark.com/estore/shop/donation-sample/ for the donation page example. (You can even download the ready made page if it suits your needs).
Another option is Donations Pro https://ignitewoo.com/woocommerce-extensions-plugins/woocommerce-donations/ which lets you set suggested and minimum amounts.
Any other ideas, please let us know…