Awesome, your making your own cosplay. I'm happy for you. It's so much fun.
I do the same. I made these guys costumes. :3
Gee, buttons. I used these fancy silver buttons I found a discount store. They don't look exactly like the ones on the uniforms but they work out.
Fabric, I used solid black cotton fabric. It's not very see through and since it was summer when these guys wore them, it wasn't that hot in them.
For the cross, I made my own pattern by drawing the shape on a piece of paper and cut it out on grey felt. After I sewed it to the coat I had my brother draw the design on the cross since I'm no good at detailed drawing.
I think I'll take pics of the buttons and cross so you can see what I mean. ^_^'