generate alternate sitemap limited to localization

[farhadrifaldi]

Hi.
I'd like to add some alternate sitemap like this
<xhtml:link rel="alternate" media="only screen and (max-width: 640px)" href="http://m.example.com" />

But in this package for adding alternate is limited for localization. like this example
<xhtml:link rel="alternate" hreflang="US" href="https://example.com/es-US" />

Is there any work around to adding alternate site like I said before? or some function that more general to use when add alternate site?