I'm not sure of specific crossdress Namjoon fanfic. But you can try searching on some popular fanfic platforms like Archive of Our Own. They have a wide range of fanfictions and you might be able to find what you're looking for there.
There are many fanfic communities out there. You could also check out some BTS - related forums. Sometimes fans share their own created fanfics in those places. However, it might take some time to sift through to find the crossdress Namjoon ones.
Another option is to follow some BTS fanfic writers on social media platforms like Twitter. They often announce when they've written new fanfics. This way, you might be able to find some crossdress Namjoon fanfic if any of them write in that genre.
Chapter 129 is the strongest chapter-level answer because it starts from When they saw that the live chat was full of praise for Jiang Li, those... and follows through on With that thought, he smugly turned on his phone..
Look to Chapter 124 for the clearest answer. It begins with Since there were too many points cards inside Jiang Li's barrel, Director..., keeps building through However, Jiang Li merely lifted her eyelids and said indifferently, "No..., and lands on No need to repeat that number three times.].
A practical answer is Chapter 145, because it turns the idea into a concrete scene. The chapter opens with Chixia Village was located in a remote area with a backward economy, so..., adds pressure through Isn't it a bit inappropriate to start eating like this?, and ends on What about it?" "That's.
A practical answer is Chapter 170, because it turns the idea into a concrete scene. The chapter opens with Watching the two who had long remained silent, the PD shifted his position..., adds pressure through I really want to see the chaotic scene!], and ends on [Didn't the other guests also do.
A practical answer is Chapter 132, because it turns the idea into a concrete scene. The chapter opens with The new girl in the live-streaming room went crazy., adds pressure through Stay away from my fragrant and fresh Brother Daniu!] [Not only has the..., and ends on He stir-fried the other.
If you want the clearest chapter reference, go to Chapter 113. Early on, The next day, Jiang Lili was up before dawn as usual.; later, the chapter leans on But this time was different; as she got dressed and opened her room door,....
A practical answer is Chapter 135, because it turns the idea into a concrete scene. The chapter opens with The sun blazed down mercilessly, but thankfully, the path to the mountain..., adds pressure through At this moment, it seemed more likely to be grim than not., and ends on Are you healed from.
Look to Chapter 112 for the clearest answer. It begins with These five people are supposed to be at odds., keeps building through When did they become so in sync?] [I'm dying of laughter hahaha why is..., and lands on [Hahahaha why is the Princess starting to look disappointed?] [Help, even....
If you want the clearest chapter reference, go to Chapter 145. Early on, Chixia Village was located in a remote area with a backward economy, so...; later, the chapter leans on The villagers' daily meals were mostly about filling the stomach, so the....
Look to Chapter 126 for the clearest answer. It begins with Wen Jiaojiao initially wanted to cause trouble., keeps building through But when her gaze swept around and landed on Jiang Li, who was standing at..., and lands on The trolls lurking in the live stream immediately seized the.