It's probably a bit late to chip in on this one from the OP's point of view, but for anybody looking for a really light shaving kit when I go backpacking I use a Merkur 45 bakelite razor and Somersets shaving oil, followed by some Lucky Tiger balm carried in a little Nalgene bottle. The oil isn't as good as a proper lather but does the job. The Merkur razor weighs well under 30g and is excellent, as is the Lucky Tiger