Even 'normal' sized people can have a hard time finding clothes that fit. In my country, it's ridiculously difficult to find clothes if you're 'in between' normal sizes and plus sizes. There's a weird gap that you fall into, normal sizing doesn't want to know you because you're a fat fuck, plus sizes don't want to know you because you're a skinny bitch.
That reminds me of a LiveJournal community from ages ago called Inbetweenies, which was made up of smallfat women in this exact predicament (after they got scolded out of the Fatshionista LJ community for being icky privileged smallfats).
As for Juliana, the issue isn't that she can't find any clothes at all to fit on her body, because she still can. I've seen men's t-shirts and sweatpants in sizes up to 8XL, and she's not there yet. She doesn't even need to sew in order to hem pants that are too long; there's iron-on tape that will do the job well enough.
No, the issue is not the availability of basic clothing to cover one's body—it never is with any of these fats. Only at the most extreme upper reaches of fatness do they size out of absolutely everything (I mean shit, look at FatLip Ash, who can still find clothes), and at that point they're bedbound, so a sheet will suffice. The endless whining about "lack of availability" for supersized clothes is strictly about consumerist aesthetics and identity—nothing more. Juliana wants more choices of clothes that she can use to prop up her "trans masc" identity and look (at least in her mind) a certain way, and she's not satisfied with the selection available to her. She's a very short, extremely fat woman complaining that men's clothing manufacturers don't take her size into consideration and make clothes to fit her so she can look the way she wants to.
It's just the most infantile narcissism, focused solely on the fatty's wants, with absolutely no understanding of any of the practical realities behind manufacturing clothes for extreme outlier sizes. And they don't
want to understand; they just want access to all the same "cute" clothes that skinny girls get, at the same price, and have turned it into a political and moral issue and proof of their oppression (while conveniently ignoring all of the real political and moral issues and oppression that plague the manufacture of cheap clothes in the first place, but that's a whole 'nother issue so I'll just leave it at that).