In particular, the store of one POP Goes the MONKEY (spelt like that) aka Matt Sweitzer. Shapeways is a digital marketplace for 3D printed products and there are so many knock-off bits for 40k.
I am serious, if there is a super obscure Space Marine chapter that you love and you want an army but you can't freehand the chapter emblem to save your life just go on Shapeways. They're all there! I am perfectly serious. Most of them, in fact, are available from this POP fellow. His store is actually pretty well laid out because, obviously, none of these shoulder pad and insignia sets have the right names because of trademark law so it can take some searching.
However, POP Goes the Monkey sorts their insignia by not only by armour mark but by general categories of the emblem: animals, body parts, general shapes and the like.
He also does mixed sets for Deathwatch armies. Previously they were ten assorted chapter-specific shoulder pads but he also has this...
… which contains thirty distinct chapter heraldry designed to be glued onto the shoulder pad. Okay, some of them are ones from the Deathwatch Kill-team set itself but alternate uses can always be found. That Ultramarines ultra? Stick it onto the shoulder pad upside down and you have the Sons Of Orar. Do that same thing and shave the wings off that Angels Sanguine skull at the bottom? Stuck it in the middle of the upside down ultra and you have the Omega Marines.
Plus, it has the Rainbow Warriors chapter badge. That deserves a recommendation all on its own.
Once these arrive I'm going to have to trawl Lexicanum to see if any of the doubles can be used for alternate chapters (the Guardians of the Covenant crossed swords can also be used for Sable Swords, for instance). Hopefully this “Deathwatch Set1” will be just the first of several such deals. Not that I'll be in any hurry, I can likely get four or five Kill-Teams out of this set.