Here's a revised list. We don't really need much, as you can see. If you feel called to find something from this list, where possible, please try to find it second-hand or made sustainably (green, fair-trade, etc.). Things that have to be new are noted as such.
pumpkin seat: lovely and surprising gift card from CCM tech theatre department will cover mostly
extra "landing pad": see above
changing table pad: probably needs to be new. It's the squishy, mattress-y thing you put on a changing table, not the cover. I like the ones that are kind of scoop-shaped. It looks like this but that's not the product--that's a cover. We have plenty of those...
sleepers/onesies: cute ones for boys ages 0-3 months (not very many of those, since he's so enormous), ages 3-6 months, and 6-9 months