Sideshow doesn't get too creative yet with 12" figures. To pull her off wouldn't be like putting clothes on a buck body. It would be more like putting armor onto a female figure, except that to pull it off right, everything, including the underbody would have to be clear cast. It would be a logistics nightmare. I think Hot Toys could pull it off, but even they might not be able to get it quite right, but then we're talkin' Hot Toys here.
Sideshow made the right call doing the maquette. I just wish I could afford it.
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Horizon Models made a 1/6 SIL model back in the day. It was very good.
The box says 1/8, but standing upright like I reposed her, she is about 12". Mine not pictured.
I did a lot of customizing on mine, including standing her upright, and having her feeding herself from one of her breast tubes like on the Giger Species cover, but I never got around to painting her. I'd take pics of it for you if it weren't buried on the bottem shelf behind the filing cabinet right now.