How do I make a Pantry door without tearing out the wall

You can make a curtain.

Check salvage stores for doors that might work with your decor.

Build a frame and put frosted glass in it.

It shouldn't cost a lot to just make a simple door. The part that might be hard will be hinges. Decide what kind you want to use and plan for them when you have the wood cut. Regular door hinges are usually inset into the wood of the door frame and the door. You might be able to use cabinet hinges since the door won't be that heavy. Plus you need to decide do you want the door within the opening or will it cover the opening? It looks like you could do either.

Get a plain piece of wood cut to size. Decorate it with some prefab trim from the lumber yard (home depot, lowes etc all carry various lengths and sizes with all kinds of designs) just select something you think will go with what you have. I'd paint it white to match the walls so the trim wouldn't have to match the kitchen cabinets. A handle that matches your cabinets or not and viola!

https://www.pinterest.com/pin/422494008764626401/

https://www.google.com/search?q=diy+pantry+door&sa=X&tbm=isch&tbo=u&source=univ&ved=2ahUKEwicufqds6ndAhUMna0KHZ4QCwUQsAR6BAgFEAE&biw=1536&bih=740

https://youtu.be/-9UwXOzmIEo or you could buy a salvaged door from a yard sale or a Habitat For Humanity type store. Simply cut it to the size you need & reattach the hinges to hang it.

A curtain hung from a swing-arm rod would make for ease of access. Drapery weights at the hem would keep it tidy.

what about something like these i have seen them made by diyers using a tall bookcase and rollers added to base