Desert lizards.... Duvet Cover

I was so excited to find a duvet cover with a bearded dragon on it for my son. Even though I ordered it early and it was promised (multiple times) to arrive in time for Christmas, it did not. When it did finally get here, imagine our disappointment when we discovered that it is such an odd size, it's impossible to find a duvet to put inside it. The description said it is 79"x79" (which is a strange enough size anyway, as typically Full size duvets are 88"x88" or 90"x90"), but the actual product is not the promised size. It is closer to 73"x78". If anyone can find a duvet that size, please tell me where! I've scoured the internet and have had no luck. So now my son has a super cool bearded dragon duvet cover that he loves, sitting folded up on his dresser while we try to figure out a solution to make it usable.