My grandfather was a golden gloves boxing coach, and he once showed me an image of him in the gym back in the 1940s carrying an amazing leather medicine ball. I, of course, asked him if he still had it. Unfortunately, he said that he it lent to a fellow trainer who skipped town. Grandpa Melzer swore he would give the guy a good "pole-axing" if he ever found him—that was his favorite medicine ball. I'm still looking for it ... but you can find some great looking ones at flea markets and on eBay.
Prices from $18 on eBay.