Any way you could educate him that he's fully protected by credit card and not liable for any charges? That's really the best answer. Banks generally back you up as well, but IIRC, they aren't actually required to do so with debit card fraud.
If he's dead set on a reloadable debit, check out the Walmart MoneyCard. No real fees.
https://www.walmartmoneycard.com/
And I would stay away from buying an Vanilla, MetaBank, or any other prepaid gift cards. Again, you'll most likely be made whole in the case of fraud, but its likely going to be a ton of phone calls.