Someone with a xapo account can help me here if he/she already have balance there and is not planning to withdraw soon.
It's possible if you pay someone in fiat through whatever payment service, and have that person then send you the fee amount through Xapo (internal transactions are free), where after that you can purchase whatever service you need. If you think that's doable for you, then look in the currency exchange section to see if someone is able/willing to help you out. If you don't plan to pay for someone to send you coins through Xapo, then you'll be in a very difficult position.
I think this solution is kinda too complicated, it's too much hassle to send ~$20 - I think that simplicity and time is more important than complex workaround.
The sooner Op will realize that sending Bitcoin is not free the better, this is the price we must pay for having a decentralized network.
Miners are not a charity they won't process our transactions for free, Xapo with its 'promotional' free BTW transaction just spoiled many new users.