Lia's in Friendship Heights has them, and does them rather well; Cleveland Park Bar and Grill (which, IMHO, has decent pizza as well) also makes them, although not excessively well.
I've been racking my brain because I knew I had seen it on a few menus lately and then I checked out the PS7 lounge menu. I haven't tried it there before but it sounds really good. Nice excuse to check out a really good restaurant.
I've tried the arancini at Locanda - it's got small, fresh pieces of yellow squash. Nicely fried, not too greasy. I believe there were three golf-ball sized pieces to an order.