We're not exclusively a Halo group, but that is the primary focus. Your particular question would probably be best to post in the "Pepakura Request" thread. Select the "Costumes and Props" tab at the top of the page, click "3D Modeling" in the drop-down menu, and you'll find the Pepakura Requests sticky. Also be sure to make use of the search bar to see if what you are looking for already exists within the forums. Also check out the "New Recruits" forum, also under the Costumes and Props tab for several help threads covering a variety of topics, from tips and tutorials on working with different materials to general help in getting the most out of the resources available on site.
As for the particular armor you're looking for, the best way to speed things along as far as requesting a 3D model is to have a full front, side, and back view, similar to
this format . It's best to avoid action/dynamic poses, 3/4 views, etc.. With flat-on front, side, and back views it is much easier for a modeler to drop the reference sheet into their modeling software and essentially "trace" and build up the model pulling proportions directly from the reference material. With non-static poses, such as the image you have provided, it becomes necessary for the modelers to free-hand and make guesses at armor contours and shapes, which not only makes the entire process slower, but leaves it open for inaccuracy. Some modelers won't even take on a request unless a static reference sheet is provided because it becomes too much of a hassle and is too time consuming. After all, the number of requests greatly outweighs the number of modelers, and they do have lives and projects of their own, so anything that can help speed up the process is a good thing.
Best of luck on your search. Looking forward to seeing a build thread from you.