You know, it is school supply season and I bet a zip up pencil case with an outer net pocket or something similar will do the same thing for about a dollar or two. I'm going shopping today to have a look for an alternative. Maybe a mountaineering supply shop will have something even more durable for under 20.00. I'll look for some case liner alternatives while I'm there.
Cabella's has something like this for example. http://www.cabelas.com/catalog/produ...AL%3BIK-580418