I have gotten three packages in the last three days, so I give you...
Pants - olive drab vietnam fatigue pants
For the price that I found them on ebay, it was not worth the time, effort or fabric purchase of actually making them myself. Not to mention a heck of a lot simpler to just buy them. Also lucky in that they come in a wide range of sizes. The only way that you would run into a problem is if you are a petite woman. Mine have cost me under $40AUD.
Shirt - black t-shirt
This one didn't come from ebay. I ducked over to Big-W in my lunch hour and picked up a plain black bonds t-shirt. You can really go with anything that you want. Just as long as it is a black knit shirt. It should be slightly form-fitting and not swallow you whole, but as long as you are comfortable. It varies in the show, sometimes they wear short sleeve, sometimes long sleeve or 3/4 and sometime a tank top style. Really you should be able to get something for under $20.
The jacket - olive drab G-8 WEP jacket.
I have found quite a few on ebay made by scifi-hero. From what I have ready these are pretty screen accurate. Normally I would make the clothing pieces, but after looking at how they are made, not to mention trying to find the correct fabrics, it is just so much simpler to just purchase. If you are looking at making the jacket, the sort of fabric you want is cotton ripstop (sometimes called ribstop) it has a square pattern woven into the fabric. And you are after an olive drab fabric. One of the other advantages of purchase a pre-made one is that it already has the velcro swatches on it for the badges that you need to attach. It is also a lot more complex than I expected, with all the detail ribbing, pockets and zips. Mine has cost me around the $250 AUD mark and I think it was well spent.
Now we start getting into some of the detail bits and pieces of the costume. The thing I love about having a tactical vest for my costume is that it has heaps of pockets. There is no need for me to carry around a bag while at a con, or try and build pockets into my costume because they are legitimately there. I bought my vest through here (the vest guy). It looks great and they have a wide range of sizes available but you may run into problems if you are really petite. I was really surprised of the fabric that they are made - it is a plastic like net sort of thing. I guess that means that it will breathe, but it was definitely not what I expected. These ended up costing around $160AUD
The holster came from the same place that I bought the tactical vest. (link) One of the best things is that they have holsters for left and right handed people, so you can get one that suits you. This quite simply hangs off the belt and clips around the upper thigh. This one cost me about $55AUD.
The tac came from the vest guy again (link) and only set me back about $50AUD. I probably could have whipped up something appropriate myself but I think it would have taken quite a bit of playing around to get exactly what I wanted, so it was just easier to purchase this, and it seemed prudent as I was already putting in an order to just add a little more. The way I see it, I am already paying for shipping, so I may as well just add in the extra lightweight items as well.
Again, ebay saved my on the zat gun, though I did get this a while ago. From what I have found there aren't that many people out there casting zat guns, but I did find one seller on ebay who sells a whole range of cast movie and tv replica weapons. They are unfinished and unpainted, so you will need to do a little research on what the finished paint job should look like, but if you are desperate for a zat, this would be one of the best ways to get one. I will worn you though, that they do seem to be picked up quite quickly, so you may have to bid a bit higher to get what you want. I spent around the $80 mark to get mine. This is the seller (link). Now I just have do the actual painting on my own.