As far as I know the Koster conversions are still available. Greatmodels.com still lists the Koster kits and conversions on their site. I purchased the N conversion set from them a couple years ago with no issues. No, I haven't started it yet, but in the box it looks very good. For me it will be a good thing to try to get my feet wet with vac form.
I've been told you can also purchase Koster items directly from Bill Koster as well, but he doesn't have a web site. Unfortunately, I do not have his email address, or I would let you have it. He has been known to check out the Plane Talking forum over at Hyperscale.com, and someone there can most likely supply his email address if you would like to go that route.
The old MPM vac kits of the Do217's are also pretty good if you can find them. They turn up from time to time at shows and swap meets.
Good luck on your quest.
Regards,
David