If you haven't already checked on eBay, it seems like someone's always listing those - deer, elk, you name it. And I'd bet some of those listing would sell larger pieces if you contact them. That's where I've picked mine up, except for some I literally picked up (deer hair) last year close to the Touchet River.
If by bulk you mean more than what's usually offered on eBay, I'm sure you'll get better answers than this.
But you know, thirty to fifty square inches of that stuff lasts a LONG time.:rofl
As a fly tier...its always good to have friends that are successful hunters. You could also check with your local game warden. He more than likely knows either someone, or has access to hides that were possible confiscated game animals, road kills, or whatever.
I've got some left over light rump hair and flank hair, nice long stuff. The patches are probably 6x6 or 6x8 inches. If you pay for the shipping you can have it. I've got more than I can possibly use. Drop me an e-mail.
FOR FURTHER INFORMATION ON WHAT I CARRY, YOU
CAN REACH ME AT: firstname.lastname@example.org . PLEASE
LET ME KNOW WHAT YOU ARE LOOKING FOR IN TERMS OF
SPECIES/KINDS OF DEER, AND ELK; AND THE SIZES
YOU ARE LOOKING FOR? I AM SOMEWHAT LOW IN STOCK
FOR ELK IN LARGE SIZES, BUT I DO CARRY A LOT OF
SMALLER SIZES--BOTH NATURAL AND DYED. ONCE I
FIND OUT WHAT YOUR SPECIFIC NEEDS ARE, I WILL
SEARCH MY STOCK TO SEE WHAT IS AVAILABLE.
The best patches of elk hair I've ever purchased came from Blue Ribbon Flies, a shop in West Yellowsont, Montana. Craig Matthews and his staff tan, dye and cut the elk hair into perfectly colored and generously size pieces. BRF has a web site, I believe. I usually stop by when we make our tour through Montana in the summer and stock up.