Hello Helena,
At the moment all of our time goes into the development of Project Fire, a brand new 4.3.4 realm. This realm will replace Reaper. Therefore your suggestion to add a shaman weapon to our current custom weapons will not happen. There will be no more new content for the current Reaper as we are focusing on Project Fire. As Dazanley already told you, you can choose to purchase VIP 1 for $10,- after which you'll have the ability to learn all weapon skills.
We will take your suggestion into consideration for the new realm. This suggestions will probably get accepted which means there will be an upgradable shaman weapon available after the release.
For now, try to hang in there using the farmable weapons, the slightly more expensive vote weapons or get VIP and use the thunderfury anyway.
Thanks,
Rick.