The only place on the internet I've found them is Australia. They do not ship outside of that country.
The company that made those leaves no longer manufactures them, and all of the known old stock elsewhere has been bought out. Even in the US you can't find them online. Your best bet is to check local archery (since I suppose you don't have firearm...) stores in the camo section. Another option is a home goods store where decorative leaves and such are sold. Those will likely need extra work to get the proper color and texture you want.
our Archery stores are mostly Olympic Target shooters as bowhunting ceased in 1981 (partly why Horton and Barnett went stateside)
Good call though.
We have more firearms dealers than Archery and can have guns up to .50cal just loads of paperwork and security checks and cost of alarms and safes etc etc