Adding donation option to the products field

How do I add a donation or "OTHER" button for a sponsor that will allow the registrant to plug in whatever amount they'd like to donate or allow a sponsor to plug in a whatever price they'd like and in turn calculate it in the total at the bottom of the page please? Thanks!

Thank you for contacting us.

It is possible to add a product with a $1.00 price and a custom quantity input.

Example:

Set the quantity selector to the Text Box field type.

If you need any further assistance, please let us know.