Welcome to the 405th! Congrats on starting your first build thread!
I really like the armour you’re going to be building (especially the cat ears XD).
Unfortunately I haven’t seen any foam files for those two pieces you mentioned floating around the 405th… that’s part of the reason my suit is entirely default. However, if I were making your suit this is what I would try:
I would try making those pieces (the hand plate and the shoulder) using foam from scratch. Because the shoulder geometry is relatively simple, I think it would be very possible to use only a few foam pieces to create without a template. A foam template for the bicep already exists and can be found in “the armoury”. So you would only need to create the shoulder bit that connects to it.
As for the hand plate, it will take a bit of guess work. I think that with one piece of half inch foam, you could use angled cuts to create the part that goes on the back side of the palm, and do the same but with a smaller bits of foam for each of the fingers.
If you’ve never don’t foam work before, don’t worry! It’s not so bad. You can use floor mats bought from a local hardware store, and a box knife or utility knife with a nice sharp blade. If you’re only doing a few pieces out of foam and printing the rest, you’ll probably be fine using hot glue, although I personally use and recommend barge contact cement foam work.
Best of luck!