I have used something like this in the past:
Sorry about the fruit salad... Blame 'sublime text'.
Some notes:
1). If you are going to put this inside the root target folder and run it from there you can delete the 'CD' line command.
2). If your working directory is not the 'OS' drive then you need to add '/D' after 'CD' so it will become 'CD /D E:\test_folder\'.
3). I am sure you are well-aware that *.* is the wildcard for any, if you want a specific file-extension then change it. e.g. *.txt.
4). The size variable is in bytes.
5). LEQ ( <= ) is less-than-or-equal. You can also use EQU ( == ) equal, NEQ ( != ) not-equal, LSS ( < ) less-than, GTR ( > ) greater-than GEQ ( >= ) greater-than-or-equal.
Depending on your preferences this .bat file may need altering.
This is a pretty good website for commands, descriptions and usages:
ss64.com