At today’s prices , you may as well just chop down a maple tree.
Meh. You don't bother discussing gunstock blanks with the sellers of wood, you just tell them what size, and grade of wood, roughly, you are looking for, and whether they or anyone they know, may be able to provide.
As to costs, they are what they are, and as long as the Customer both wants and is willing to pay, it's of no consequence.
IF the Customer is NOT willing to pay, then you discuss potential alternatives.
For the OP, I doubt there is much more than a few dabblers in the gunstock supply world around Canada, mostly guys dealing in Turkish, English, and other imported walnut blanks in small numbers.
But there are a fair few hardwood suppliers to the furniture and custom cabinetry trade that are like to be able to hook you up! It's just a block of wood, until you carve it into something!