BIG BABY- DIAPERS?!

Brit

Help! My 9 month old is just about 40 pounds. He's perfectly healthy (doctor has double checked) he just never has grown out of the eating every 3 hour phase and loves all food! Plus his daddy is a big guy and was a big baby! But he's just about outgrown size 6 diapers and is nearing the need for size 7s. I've been having a hard time figuring out what to do when he outgrows the 7s. He seems to be going through a size every 4-6 weeks. I can't seem to find cloth diapers that go bigger than 35 pounds without being the grown adult sizes and am afraid he would be too small and adult or older child ones wouldn't fit right length-wise. Any other parents go through this? What did you do?! (Also I am in the US. I know they make size 8 but they only sell them in the UK it looks like.) Thanks!