Yup, what Magnus said. Also, check out Leg XX's website, they have a list on how to MAKE all of this stuff, it's not as complicated as it seems, just takes time and diligence. Also has a great list of acceptable and not-acceptable stuff that's out there.
The good news is that many of the items can be modified to fit and look better, ie the Deepeeka segmentata won't fit everyone well, and the leather harness straps may fall apart before too long, but they are fairly easy to replace (again, just time and effort)
www.larp.com/legioxx.html
I've always nudged my fellow members in Leg. III Cyrenaica to make their own belts, which is also pretty easy to do. Buckles are tricky, even for me, but people like Raymond's Quiet Press and Clang Armory are affordable and really good. Grab some thin brass sheet at a hobby store or online, and a nail-set, and you can punch designs into belt plates in a weekend.
Also, please please do not be offended, but your icon image is from the Museum Replicas catalog of the Worst Piece Of S--segmentata Ever Constructed. I say this because that was the first armor I wore and it was an awful experience. It took like 3 people to hold me down and tie me into that thing, and I had very limited flexibility. No, really.
...Plates were thick enough to be bullet proof, corners/edges stuck into areas of my body that were not acceptable, etc...
Everything Greek/"Spartan" and Roman in that catalog is total Junk. Not even worth the price for display, if you're trying for accuracy.