Thank you for the suggestions everyone!
Sabine, thanks... I'll look into OCK (I've never actually heard of them.)
David, I have tried Mammut and Rab and I currently own a small Microlight Alpine and a small Infinity jacket, but they are both a size to two sizes larger than what I should be wearing, so layering isn't work well. The chest on a Rab XS is 35.5" and my chest is 30". While I am very please with the quality of both jackets, I just find it strange that Rab advertises XS in their fit guide, but I can't ever find any garments on their site that they actually produce in an XS. I wrote them months ago asking about extra smalls, but never received a reply. I would love to give their Meco line a try, but their small tops are two sizes to large for me and their pants are 3" too large in the waist, so I've given up the idea. Having tried multiple tops from Mammut, I've had the same problem. Thank you for the suggestions though.
Andrew, I have a good friend that works for Columbia and Mountain Hardwear and she asked around internally and they just recommended trying to get by with youth sizing. If it's a close fit body and waist wise, the arm and leg lengths are comically short and the garments aren't nearly the same quality or as technical as the adult versions. I may combine your idea and Nick's and have my tailor tweak a couple pairs Mountain Hardwear pants for me. :^)
Nick, I've gone the special order route with both outdoor suppliers in town and in Asheville and they've given up trying to find extra smalls that fit from Mountain Hardwear, North Face, Patagonia (makes xs in some garments but they're sleeves are incredibly short in that size,) Arc'teryx... just to entertain them, I've tried on my fare share of youth clothes with no luck as well, without luck. I've got some great recommendations for casual/designer clothing if you're children are interested (pm me) and I think I may start saving for some Beyond base layers and have them tailored correctly from the start.
Thanks again everyone. I really appreciate the ideas and responses.