Please forgive me for posting a question about a non-nikon product, but I thought I had a better chance of getting an answer here than anywhere else. I use an old Cokin three head ring flash with my D80, but I discovered that only two of the heads are firing. This seems to mean a blown flash tube. Does anyone know where I can buy another tube, so I can replace it myself? Shipping the whole unit to and from a repair facility would be cost prohibitive in my area, Panama. I hope to find a tube from someplace that does not require a large minimum order, or a high shipping cost.