Yeah V, unfortunately it's a character thing, so it has to be dark blue or it's not the right costume at all--it would be like dressing up as cookie monster, but using brown fuzz.
The khaki suit in foot's link might take blue dye nicely...
This is exactly what I need. It's made by Dickies, but for some reason it's only sold in their UK stores, not the US. I've got an email into their customer service department to see if they can ship one to an American Dickies outlet for less than $20 (which is what a variety of resellers of that item generally are charging.)