For the shirts: White shirts, maybe one size bigger than your usual one (they seem to be pretty beggy), for the blue parts, there's shirt textiles that come in already cut-out parts of ~10 to 15cm which can be easily hand-sewn onto the shirt (make sure to stretch them a little while pinning them to it before sewing them to the shirts sleeves, that will make the puffy sleeves). - aaah I run out of words here, but there's a really easy thing to make them look like they don't have any seaming on the outside, for that you have to look up on a tutorial, I don't know how it is called in English ;w;
for the pants, same thing, but with un-stretchy ribbons that come on rolls (bias binding) on a pair of un-stretchy blue throusers in the same color of the sleeve-add-ons. simly sew them on there by hand, since machines can be horrible when sewing something down a leg.
That's it! For the shoes, I am sure you can find them on ebay!