I bought a twin-size cot with an air mattress last summer and after using it for less than 10 days, it has a leak in the air mattress. Of course, I didn't find this out until a few days ago-well after any guarantee would apply. Does anyone know of a place to buy JUST the air mattress? A regular twin size mattress is way too big. I hate to buy a whole new cot-not only for the expense, but then I'd have the cot part leftover and it can't be used alone. Any help would be greatly appreciated. I'm going on a mission trip this summer and we stay in schools so I need a good cot. Thanks!