I was shopping around at my local Supergo (I know, no taste, hey pass the Fritos) and getting over by the mtb stuff I noticed a Specialized "Large Universal Slap Jacket", SKU # 9894-2315. It immediately struck me as the thinner, lighter, strap pad for my Timbuk2 messy bag so I tried it out, hey it fits! The Timbuk2 strap is thick, I think too thick. And yet, when there's 20 lbs of electronics junk, groceries, etc in the bag you sure want some padding.
This thing is great! It's meant for "Oversized aluminum chainstays and swingarms", yeah, whatever you springloaded pervs, it makes a great pad - it has some antislip stuff on it so it won't slide around, and the Specialized S hides on the inner side against your shirt. Oh, and it was $10, and hey it's Specialized, can probably buy one a lot of places.
(I'm still working on a way to optimize/replace the Timbuk2 cam lock thingie, I'm getting tired of seeing that big LOOP in my shadow when I ride, gimme some time.)