How big are your buns? I got a wonderful carrier bag for Sinterklaas: it has a sturdy bottom but a semi flexible top, and there are 4 different zippers.
One side opens fully, the other side opens halfway like a barn door, there’s a zipper that opens the whole top, and a small zipper in a side panel so you can stick your hand through to pet your bunnies.
This is the model I use, but there are several sizes. I love this one because it’s small enough to carry on my lap while I ride my mobility scooter. It fits on my lap when I’m using my wheelchair as well, and I can wrap the shoulder strap around my waist to keep it in place. Both Owen and Molly fit in it with room to spare ^_^ They’re 1,4 and 1,3 kg.
https://www.bol.com/nl/nl/p/nola-coco-katten-honden-en-knaagdier-reistas-43-x-25-x-28-cm-grijs-tot-7-kg-huisdier-draagtas-knaagdier-reiskennel-reistas-kat-kattentas-transporttas-transportbox/9300000074941625/?bltgh=iwAcoFYm1-JeADBHcKdL3w.4_28.38.ProductPageUrl