Hi there Razza,
Depends on your finances.
If you are looking at second hand, I would try WindSurfnSnow in Sydney. They usually have some reasonably good quality used masts and booms. (I do worry about the life left in some of these though). But they are a cheaper alternative and will do the job for a while. Don't forget to look at the second hand ads on this site. Trouble here is you can't see the quality of the gear. Be careful....
If you are able to afford it, then new a mast and boom from say windsurfingsales.com.au is worth a look. I think you would need a 460 mast and an adjustable alloy boom say 160-210cm. Their range of product is good and I do use their booms. You may also get a package deal. Try it. Should suit sails you have.
(I am not sponsored or associated with either of these places in any way).
PS: I have 2 NP sails (6.5 & 7.5) and a NP 460 X6 mast with Loft & Gun booms. Thought the NP booms were too expensive for what I do, plus have heard of some problems with their newer booms. My old NP X3 let go one day while sailing off Jimmy's Beach which resulted in a 20 minute swim back to shore. Not far but difficult. Didn't hear any "duh-dah" music so I was lucky!! Gone off NP booms since then.
Good luck.