A pretty simple custom model of a sickle
The mpq has everything you need, just extract it into your data folder. Then open it with my warcraft studio and rename the Insert_Name_Of_Item_To_Be_Replaced_Here.m2 to match the .m2 of whichever weapon you want it to replace (e.g. Sword_1H_Raid_D_06.m2).
If for whatever reason you need the .m2 and .blp, they are in the zip file as well.
Download link:
RapidShare: Easy Filehosting