Only a credit card is accepted by eBay to verify your age.
The only workaround is to ask a friend / family member who does have a c. card on their eBay account to buy this item for you. A faff I know and many are faced with this.
Currently, only a (single monthly payment) Credit Card entry to confirm your age is acceptable to eBay --- nothing else will do !! --- an everyday use Debit Card will not be accepted.