Well, CSS still seem to list MA drivers:
http://www.creativesound.ca/products.php?make=MarkAudio -there's also a moderately sized logo on the left hand side of their homepage.
Dave does only advertise his modified units, but if he has any he hasn't got around to modifying yet, he'll no doubt sell them if you ask. No idea about Solen. Madisound have simply sold out, although my spies tell me they should get some more stock in soon.
MA drivers are made in relatively limited production batches since they're a very small company who produce all of the components themselves, or have them made to their design and tolerance requirements. AFAIK, the only 'off the shelf' component is the magnet, everything else is custom. As a result, sometimes the main dealers can run out for short periods; the up-side is that since the drivers are usually recieve an update every 2 years or so, you're usually getting the latest model. I believe there are a couple of new units in the offing too. Mark is currently recovering from an operation to remove a tumour -since he's been very hands on to date, and the company is very small, this has probably held up producution slightly. The good news on that score is that he's making good progress -there's a thread on his own forum.
