There are walkthroughs ( GameFAQs etc ) that list all DKS armor set and weapon locations.
I remember being able to buy some but also having to quest for others...Necklace on marker, boss loot or hard jumping / fighting deals.
I checked at GameFaqs, but the only FAQ that lists it doesn't list locations for the DLC armor sets, just the ones that came with Ego Draconis.