Maybe this answer is a bit too late, but I thought I should add my two cents.
Have you been looking for US or Norwegian sources? There are many companies and organisations in Norway dedicated to bunader. Most do, as you say, mostly seem to sell finished garments or kits, but if you contact them they should be able to either provide patterns or be able to point you in the right direction, e.g. to pattern books. It's worth a try if you haven't already.
Sometimes the use of pattern in folk costumes are really strict (especially goes for the reconstructed bunader where the patterns are actually owned by the regional bunad organisations) and have to follow certain rules so that might be why just finding patterns is so hard. Also, a lot of people probably prefer complete kits, considering that costumes often need special fabrics or ribbons you can't find in the local fabric shop (and because it's very nifty to get fabric with printed embroidery patterns on).
I'm Swedish so I'm not that familiar with norwegian costumes, but I have a copy of the magazine Bunad, in which you can find many resources listed. I assume you have already found them (or most of them) on you own but if not here's a list: http://bunadogfolkedrakt.no/http://www.bunadraadet.no/
Here's a link to the magazine: http://www.bunad-magasinet.no/
Another resource with lots of pics: http://www.scandinavianfolklore.com/
(despite the name it's pretty much just about Scandinavian folk costumes, from Sapmi in the north to Denmark in the south --don't miss the blog, which is in english.)