I found some great hard pennywhistle cases — chopstick boxes. I’ve collected chopsticks for years, and always kept the boxes many come in as a just-in-case thing (no pun intended). I recently discovered they make great cases for pennywhistles.
I make hard cases from PVC pipe. I get either cork or foam from the hobby shop in 1/16" thickness to line the tube. Then I glue an end cap on one end and an adapter for a screw plug on the other. Hardware stores now carry spray paint that will stick to PVC so you can paint it any color you want. No matter what size whistle you have, the hardware store will have a PVC pipe that makes a nice-fitting case.
i use a coin case just take the coin trays out got my one at lidil for £6.99 looks like this http://www.arrowfile.com/product.asp?src=gawaff&pf_id=CAC411