The New Practical Chinese Reader introduces the following decomposition: na4 (那) = na4zi4pang2 + yi4 (阝).
I understand that 阝 represents radical 163 (yi4).
Na4zi4pang2 (pinyin) looks close to radical 74 (yue4, 月), but only close. It apparently is not a proper Chinese word or phrase that can be looked up in a dictionary.
My current guess that it is an arbitrary construct for a situation where one of the basic constituents of a composite character is not another basic character nor a radical, yet something that is also made up of strokes, and that the pinyin name is the concatenation of stroke names.
Could an expert and/or native speaker please confirm or otherwise clarify. I'm especially interested whether such constructs have Unicode font representations (and what the Unicode representation U+xxxx of na4zi4pang2 would then be).