VISA Proof of payment

Good day.

I applied for a VISA at the start of 2020 and paid for it. The Visa was issued in mid Jan, but I was not able to travel due to lockdown. The organization that had invited me to China has offered to refund my visa expenses if I can provide the official invoice from the embassy. I no longer have that and need to know who I can speak to to get a copy of that.