I really want to try and finish this Christmas event and want to buy Monkey Bucks so I can buy hammers but there is no option for that.

Is it not available yet, will it be available or am I just missing it ???

Go to the screen where you break eggs and try to break one. An option will come up to get more hammers. One of them is for monkey bucks. If you click on that, another screen will come up with the option to purchase monkey bucks.