Jonathan,
I use a fletching cover with my bow quiver all the time. I prefer white cap dips and white fletchings like a lot of the guys have mentioned. I hunt ground blinds a lot and tree stands on occasion. In both situations I remove the quiver (Boa 5-arrow) and hang it upside down to keep wet weather off the feathers.
I made my own from fleece. Easiest way I found to make them is to sew a tube big enough around to fit the quiver. Then cut an oblong piece and sew it to one end. This makes an oval, flat bottomed "bag". You can hem the edge to put elastic in or use the snazzy elastic cord.
My wife, who sews things, found some cool interfacing material that you iron on the back of cloth. It makes it a little stiffer (less likely to smoosh fletchings) and a little more water resistant. I will see if I can find some pictures.
Post us some pics when you get your's done. I'm always interested in how folks make their own stuff.
OkKeith