I may have been simply lucky that the medium silicone ones fit me perfectly. Round silicone tips don't always offer the best isolation. I would suggest getting a pair of comply tips. They make ones specifically for this model.

Ya they're not very common. At the time I'm writing this there are no reviews I can find either. Which is odd cause they're just under their top of the line K3003.

Depends on where you reside. Amazon has them, but I got mine for a better price at a local HiFi/headphone shop.

Brand AKG Model K374 Price $99 Type Universal Fit IEM Spoiler ★★★★★   What I own Shure SE535, AKG K451, AKG K374 What I used to own Klipsch S4i What I've extensively listened to Sennheiser HD800, Sennheiser HD650, Shure SE215, NuForce NE-700M, Nocs NS600, B&W P5, B&W P3 What...