where To Get Zealous Scythe and Fortitude Scythe Grip?

Where do I find: 1 Fortitude Scythe Grip and 1 Zealous Scythe? And also, how do I combine them? Also... How much does it cost and is it cheaper to buy one already made?

Best bet to buy them is in Kamadan. The fortitude mod is about 4k and the zealous mod is about 6k. You have to double click the mod once you have them and then you click the Gold or Purple scythe, since those are the only 2 colors that can be fully modded. It wouldn't be much cheaper to buy the mods already on the scythe because most sellers take those into consideration.

Just to note, I am level 9 and I only have about 700gp (I spent most of it on armor and runes!). Now what would be the best time to buy one of these (i.e. Does it have a scythe mastery requirement or something because mine is only 8?)

Nah, information about mods and many other things can be found at: http://wiki.guildwars.com/wiki/Scythe_mods