Not sure how shipping would work but in the US gift cards can be purchased at Sam's Club, Target, and Amazon. Amazon may have the best international options.
It would probably be easier to find egift cards that are e-mailed to you than to find somewhere that ships internationally. BJ's has discounted GC and you can do a free 1 day membership. There's a whole thread on Disney GC here. Start with the first post.
Thanks Wanderlust7 that sounds like the perfect option for us. I didn't know you could get them emailed that's fantastic. Our last Disney trip apart from a Disney cruise was 2017 so lots of new things to learn for this trip. Now just have to get my head around Genie +