You can get it from disassembling gear of that motif, get it out of heavy sacks and black smithing hireling bags, and possibly (although I am not 100% sure on this one) get them out of random chests. That might just be provisioning mats though.
If you want any significant number of them, your best bet is to buy them.
I find bone, (bosmer racial) and other racial crafting items while looting/ransacking houses and other buildings. As was mentioned you can also gain occasionally those items by deconstructing items from that particular racial style also.
Yup! If you're AD you can go to the bank area in Vulkhel Guard and all the chests and cabinets behind / in front of the bankers usually give me great luck with getting things like that. I always just check all those every time I go to the bank and I usually end up with enough to craft with!