Is there such thing as "active dry sourdough-variety yeast"?
No, I really don't think you can have "sourdough yeast".

If you want sourdough without the "fuss", you can look up sourdough flavor additive and see what works for you - one here, and here, just for examples.

The thing is, sourdough starter isn't just yeast, it is a complex community - including several strains of wild yeast and bacteria, and a complexity that comes from aging. Yeasts can be packaged up - though balancing several strains is tricky, especially if you want consistency - but the bacteria is a lot trickier, especially since conditions which support bacteria are easy to contaminate with the wrong strains, and you would want the product quick - so not taking the time for the bacteria to establish a strong culture, which leaves it more vulnerable to said contamination.

Bread yeast is, I think, basically what happened when sourdough yeast was cleaned up and regulated and made safe for storage.  I have heard of starters that began with commercial yeast - it apparently takes a while for the characteristic flavors to develop, but apparently they do. Also, I've heard extended proofing (cold proofing) gives more complex flavors somewhat similar to sourdough, so simple time is, in fact, a factor in how the taste forms - it gives time for the fermentation to work.

The fact that adding more time to yeast or dough makes a bread more complex and sour-dough like, makes me think that there's no way to build that flavor naturally and quickly - after all, there's no instant time on our shelves.