If you’d like a yellow hoodie like the one April wears, you have a couple of options!
I think her exact one is from Urban Outfitters (on sale for $29): they don’t have yellow online at the moment, but you can always check in-store
American Apparel for $48
Forever21 on sale for $15
H&M (no online link, but they always have them in stores - I got mine for $29)
April wears a similar camel-colored skirt in season 4 and in NBC’s Brotherhood of Man promo. In the promo she also wears a blue sleeveless blouse. You can get the similar ones at Forever 21.
April is seen wearing denim button-down tops frequently throughout season three and four. Urban Outfitters is selling a similar piece for $59.
April wears a printed v-neck top and striped cardigan in “Operation Ann”
The exact shirt has been discontinued but a similar one is now on sale from the same vendor.
April wears this Marc Jacobs tee in both “Ron and Tammys” and “The Trial of Leslie Knope”
April wears a floral Madewell dress in episode 22 “Win Lose or Draw”
While the dress is currently out of stock, here are a few similar alternatives: