Utricman,
The clone of D. slackii I grow originated in the nursery of the guy who the plant is named after, Adrian Slack, Marston's Exotics. That is where the person I obtained mine from bought their plant, several years ago, I have no further details on location, collector etc for this particular clone.
I'm not sure how much the differences that you see in my plant, compared to others you have seen, are genetic or due to the age and size of my plant and the conditions in which it grows (large pot and NZ LFS compost in particular). The leaf lamina don't look that much different in shape to those in the photo on page 132 of 'The Savage Garden' to me, though these are obviously younger plants. When I first got this plant, it looked just like any of the hundreds of D. slackii that I must seen in other collections, here in the UK, or for sale at CPS meetings and in nurseries. I am not certain that there is more than one clone of this plant in cultivation in the UK and wouldn't be suprised if they all originated with Adrian.
This plant flowers for me each year and can be coaxed into setting seed with a little help from a toothpick. However, neither myself or any of the growers that I have sent seed to in recent years have managed to germinate it, so I can't be of much help providing you with useful material from this one. I imagine that two genetically distinct clones are required to produce viable seed, either that, or I have a sterile clone.
Cheers
Vic