A little while ago I bought some RM Williams boots on Ebay that were just the style I like and were surprisingly cheap.
Small problem – they were a size too small. I could get them on, but after a couple of hours it hurt so bad I had to take them off. So I hunted around for a way to stretch them. There are lots of ideas out there, and it took a while before I found that I thought would work: rice.
Fill the front half of the boot with rice, sit the boots up against something so that the toes are pointing to the ground, and fill them with water. The rice, of course, soaks up the water and expands, and in doing so moistens the leather and helps it stretch.
I left them overnight and it worked – my boots are now a comfortable fit.