My sympathies to your husband, I have that as well. Cherry Tree is pretty widely available. I hope he was also told to stay away from shellfish (hard during crab season), organ meats and most important, drink lots of water.
Trader Joe's has some choices, I usually try to get Black Cherry juice. Make sure you check out the label and see that it is 100% cherry juice. Producers like to slip in apple and grape juice in there.