That's the perfect place to find the correct pattern. Just bring the picture in and say, "I need to know the name of a pattern for this style" and they should be able to give you a name.
By this I mean they will say look in our books on that table (and point to it) and say look under costumes then find the pattern that says this or that (in this case I said 3 musketeer) then once you find it look in the draws they have labeled for the pattern and buy the one that has your sizes.
Well I cant SHOW an example but I can explain it..First you take your sleeveless shirt (guys wear them a lot, they just look like a t-shirt but it looks like they forgot to sew the sleeves on) If you don't own one a pattern for the same type may be cheaper, but for this situation I will give you what you asked. So you trace the outline on 2 fabric pieces but make it as long as you need it), the back one will be the exact outline, the front you want to make a line in the middle (where it splits) and make the front look like the one in the picture (in this case there is no other cutting needed then just straight up the middle) then make a collar (you can get a pattern online, all you need is a picture..They aren't that hard. Then attach the collar. Then you sew the sides and top up to look like a vest. For the arrow looking details, you will need to make those in your own hand made pattern and sew it too the back (I don't know if it goes all the way to the back) and slightly to the sides then make loops for it to fit though and sew them on. The front detail I don't know what it is but I'm sure you can just make that design and sew it on..
No problem. Always good to help another cosplayer with their troubling parts ^_^