Well...do we REALLY need any of this stuff? Anyway, it depends on your budget and the level of accuracy you want to achieve. I've been working on my Fett suit for about four years, gone through several versions and upgrades, and only recently this year did I break down and buy the awesome chest display made by TK409's brother. I got to the point where my costume was complete and cool, but I just wanted to get to the next level of accuracy and coolness.
Since it is costly, I'd consider it a finishing touch, but if you're on a tight budget, I'd recommend putting your resources into more important parts first (especially a good bucket).
If you're going to rivet your armor onto your vest (which I wouldn't recommend) you wouldn't be able to access the back of the chest lights to install the battery. You'd have to cut a window into the vest behind the chest plate.
Don't rivet on the armor, either use heavy duty snaps or velcro OR you can epoxy flat-head screws onto the back of the armor, push them through small holes you cut into the vest and screw on a nut on the inside of the vest.
the reason wht i was saying that was cause i rivited my armor on the wronf vest before and i had to get a profetional to dril it out no there r litlle holes in every corner where the rivits were and i want to close them off too
Instead of spending a lot of money on some chest lights, just use that awesome tutorial on how to make your own from a bicylce light on tk409's website. That will probably do until you get the money to buy some nice ones.