Yes, Sleazy (actually, it's "real" name is Sleazy Sleepwear for Horses) is a brand. Lycra horse wear will not/should not stretch. I've had a ton of lycra products, from tail bags to hoods to full body sheets. Nothing has ever stretched.
I know lot and lots of people love "Bossy Bibs", I however have never had experience with them. Bossy's Bibs Web Site - www.bossysbibs.com
I personally am not a big fan of the Sleazy brand stuff. After using other brands, I find it to be quite inferior. I absolutely LOVE everything from Schneiders. The stuff they carry is much higher in quality. My most recent purchase (which I just received yesterday) was a fleece lined winter lycra hood, and oh my it is absolutely fabulous. I am very happy with it and I can tell it's going to be SO much more durable than one I had from Sleazy. Here's a link to their shoulder guard.
Edit: Ahh, I see you've already made a purchase. I hope it works well for you. Being under a blanket anyway, it's much more "protected" than say, a lycra hood (unless of course there's another hood over it).