I created a site for an e-portfolio using the new Google Sites. Google sites automatically generates a sitemap for you at sites.google.com/yoursite/system/feeds/sitemap, which can then be submitted via Google's "Search Console". However, I migrated to a custom URL, and so I no longer have a sitemap at that location. Google Sites does not have FTP support, and applications such as FileZilla can't access it. I have heard that SML Cloud can make up for this, but I would prefer not to pay $5 a month just for a sitemap.
One idea I had is to put my sitemap on a different domain from my site, but I am not sure if this would even work, or where I could go about doing that. Also, if I need to finish making my website and then export it to a different host somehow to be able to use FTP, then I don't mind doing that either.
Is there any way to put a sitemap on my Google Sites site that has a custom domain?