Shop your local used gun stores / pawn shops / gun shows....but you'll be very lucky to find much of anything between $ 100 - $ 200 that will fit that gun off the shelf.
Even if you wanted to carve / shape your own from a solid blank ....even a block of "ash" which is very inexpensive - would cost you at least $ 75 ...at a good lumber yard ( if you can find a block big enough and dry enough / without a lot of checks and cracks in it ....you'd be very lucky).
I laminate wood for all kinds of things - to make up large blocks ...for boxes, bowls, table tops, etc ....and you can try that - if you can plane or joint the faces clean enough to give you a good glue joint - that might work. Then bandsaw the rough size / and hand shape it from there ...( if you have a lot of time ) ....
Honestly, unless you're just looking for a wood-working project, you're better off staying with what you have on the Legacy model now ....and maybe installing a comb pad or something to adjust the fit to suit you in my opinion.
But one of these winters ---when it rains for 45 days straight ---I'll make a stock ...one of these days ... But if you go the route of making a stock / don't forget it will take some time - and some talent - to get the hole drilled for the stock bolt properly too ( the hole can be drilled on a lathe - between centers / much like you'd drill a hole for a large pepper mill ) with a long auger bit / maybe a forstner bit ....or on a big drill press ...if you could figure out a jig to hold it stationary so you could drill from both ends ( and meet in the center ) .... Making a stock is not inexpensive ...and really time consuming ...and that isn't what you asked ....but all of this relates to why stocks cost so much / even when they're machine made out of "junk wood" ...