This trend got a lot worse when China-made clothes flooded the US markets starting around 2005, because of lifting of import limits (5x-10x increase in quantity). The cheaper materials used were far more likely to contain latex-based elastic rather than synthetic alternatives. Also, the China-made clothes seem to use shorter, thinner models, which results in fit problems for me. I haven't been able to find adequate clothes since then, and was getting by on boring t-shirts and one brand of pants, but not very happy about it.
Recently, I found the following online stores which provide latex-free underwear, bras, swimwear, and some shirts.
Decent Exposures - organic and optionally latex-free clothes.
Cottonique - organic, latex-free, and optionally cotton-only clothing. Includes a drawstring bra design, as well as socks. Men's, women's, children's.
I've also found that JMS (Just My Size) white underwear seems to be latex-free. The black underwear does irritate sometimes, but white is fine. Olga bras (JC Penny's) seem to be latex-free as well. And 100% cotton Gold Toe athletic socks are fine.
Hanes and Fruit of the Loom both have caused latex allergy reactions at times, though I'm not sure whether it's all models, and Playtex bras have caused problems. Some of these might not have latex in them, but might have cross-contamination from the factory or I might be reacting to dyes or chemicals; it's hard to know. The make of elastics doesn't have to be printed on the label, so trial-and-error is the only way to figure it out (or an overt smell of latex).
SewSassy Latex-free elastic - sewing supplies. I can't seem to find these in local hobby stores so might be ordering some.
I'm also starting the process of learning to make my own clothes. Phbbttth to bad fit. Phbbbttth to never having my size. I'll start simple but I'm going to figure out how to make the things I want and will enjoy, and that will fit right. And as my size changes from weight loss, I'll make more.
I picked out a couple of Simplicity patterns, and will be starting a class every Tuesday evening (small group, private instruction) to get through all the confusing beginner steps and get figured out what I'm doing. I have way more ideas than I have skills, and if I have a mentor I think I'll make it through the process just fine. The results might even be pretty. :)
At least if I make things myself, I'll know what went into it, and be able to adjust the tricky points to my own proportions.