You could create a charity fundraiser on GoFundMe or Every.org and match the donations yourself.

If you want to automate the donation matching, I'd suggest batching the donations and only charging the fundraiser creator for the total amount every 14 days or when the fundraiser ends, rather than creating a matching transaction for every donation. That would cut down on payment processing fees.

You could also experiment with authorization holds on the user's credit card - they basically hold a certain amount of money hostage on the credit card to make sure that amount (or some lesser amount) can be charged to the card later. For example, you could authorize $200, and if the fundraiser only raises $150 by the time the hold expires, charge only $150 to the card.

There are some risks to the user that you might want to design around:

• If the fundraiser raises a lot of money (> $1000 for example), the creator will be liable for a huge donation match and may not be prepared to pay that all at once. You could set a cap on the amount that the creator pledges to match, or set up a "pay over time" option.
• If the user sets up a bank transfer or debit card as their payment method, there's a risk that the matching payments will result in an overdraft on their bank account. I'd be more comfortable using a credit card even though the processing fees are higher.