We have 1" matress toppers as well and were going to use some sheets to sew a cover for it, but we were at Target one day at came across a kids camping themed bedding set.
We bought two of the comforters and they fit perfectly over the bed area and look real nice (the colors go well with the tan interior of our TM) and my boys love the camping theme. At night, we just lay the sleeping bags on top.
More expensive than the sheets, but they go real well in the TM and are real comfortable. They're heavy/thick enough to stay in one place without having to sew a pocket around the mattress topper.
We also got the latern night-light, a couple of pillows and wall art (we use velcro to stick it to the wall) in the same theme.
Woolrich Bedding Collection