They sold 3x1 VASSBOs with glass in them. They're phasing them out though I think, you can't find them on the website or anything. There was a couple at my Ikea last time I was there though sitting next to the actual Besta Cabinets.
Hmmmmm, having 3 doors on a besta always bothered me and I've heard about the weight issues if you have all the doors open and it tipping over. Definitely going to have to anchor the besta to the wall. I think I'll try to find someone who can make something similar to the besta door but one long piece.
