I mean, Kirby is just pink and stars and stuff, can't you just improvise?
Get some cupcakes with pink frosting and some star sprinkles, pull all the yellow ones out and cover the cup cakes with yellow stars
Make your own Kirby pinata by just making a pink sphere and glue printed on details since Kirby has like the simplest face, ever. Fill it with star shaped candy. Or just buy a yellow star pinata and tell them it's a warp star
Serve blue "Dedede punch" and "Waddle Dee's favorite" which is just apple juice. Maybe get a star shaped ice cube tray from the 4th of July section of Party City and float them in the drinks
Print out a big poster and play "pin the apple on Wispy"
Get some inflatable hammers and swords to give out as favors. Maybe some cheap solid colored hats in various colors to similar Kirby's powers.
I don't know how many kids are coming or how much you want to spend,
but you could break this set up and give each kid one
Here's your decorations
https://www.partycity.com/yellow-star-balloon-115788.html#swatch
https://www.partycity.com/pink-round-balloon-45001.html
https://www.partycity.com/bright-pink-fringe-streamer-788648.html#swatch
Hot glue Wispy's face onto this:
https://www.partycity.com/metallic-palm-tree-centerpiece-25373.html
It's three black ovals and a pointed brown nose
Pink, Dark Blue, Red and Orange plates/cups/whatever to represent Kirby, Metaknight, Dedede and Waddle Dee
Get the cake topper to "ground" it as official stuff and not his parents just buying pink party supplies.
You can do this :D
My parents used to throw me whatever type of party I wanted, whether official merchandise existed, or not. I remember one year they had a big poster of Sonic printed out and bought some cheap gold rings from the dollar store and we played "pin the ring on Sonic" and you had to land it on his finger.
