A couple months back we put non standard twin bed back in our rexhall due to health problems. we bought some fitted sheets for our beds and are happy with fit and quality. Advanced Bedding have a good selection of sizes and colors 1-800-654-3365 they also have a website catoluge etc. also depending on the bunk bed size a split-queen sheet set from the big box store maybe close for fitted bottom sheets you still end up cutting the top sheet sewing hem etc. check out Advanced Bedding