I'm not ready to put him in a real bed yet (nor do I have one for him), but I had an extra long bed rail that I had used on Ava's bed. And his crib has a removable drop-side rail. The bed rail cover started falling apart after just one wash in the machine, so I figured I'd have to make another cover. I discovered, however, that the extra long rail was too long for the crib. It was a 3-piece deal but they didn't make it so you could link just 2 lengths instead of three.
I didn't photograph the process and it's hard to explain, but essentially I bought some wooden dowels and shoved them inside the hollow aluminum pipe frame then duct taped around the pipes so they couldn't slide. After all, this had to be toddler-boy-proof. I took the older cover, adjusted the length and stole the zipper from it, and traced around it onto my new fabric cover. I still can't believe how quick and easy of a fix this was. And cheap too! (about $5 total).
And here's the little trouble-maker himself, in his jammies and excited for the change. He loves being in pictures.