I was looking for speedlight barndoors and came across these from B&H a couple weeks ago SP Studio Systems 4 Leaf Barndoor Set for SP72 SPBARN72 B&H. Relatively inexpensive ($14), easy on/off, and they work very well. I've used them with my SB700s, but I'm pretty sure they'll fit SB-28s, SB800s, SB600s, etc. Not sure about SB900s though.. I'm not affiliated with B&H or the manufacturer, just a heads up if anyone is looking.