[Edited, as sugested by Gavin Simpson, this solution as a flaw since it won't work if the user rotates the device]
What you could do is use javascript to determine if the script should be loaded.
To do that, you can replace the code that you are using with the following one.
<div id = "NameXYZ">
<script>
//Determine if the device have the dissired size, information about MatchMedia here: https://developer.mozilla.org/en-US/docs/Web/API/Window/matchMedia
if (window.matchMedia("(min-width: 480px)").matches) {
//if the size matches, write the scripts to the document
document.write('<script src = "// 123.com"> </ script> ');
document.write('<script src = "// 1234.com"> </ script> ');
}
</script>
</ div>
This code will check if the sice of the screen is higher then 480px, and if it is, will return "true", so the if statment will be executed and the scripts will be included.
Hope you find this usefull.