How to shrink cotton shoes by just 1 size?

I really really really love these 100% cotton shoes i got. It's a size 7 but my true size is a 6. I can stick a finger of space into it. I want to throw it within the washer buut is there anyway for it to just shrink down one size. If so can you explain it to me? :)

thanks contained by advance!

Answers: Sorry but you can't shrink the rubber sole...

dry-clean then contained by hot water and dry, repeat as compulsory