Here are some applique patterns for a megaphone:
http://fivestarfonts.com/index.php?r...product_id=519
If you know someone who has an embroidery machine, there are a lot of embroidery patterns for megaphones that you can buy online.
Edit: Oops. That first link I posted is for an embroidery applique. All the ones I have found are for embroidery machines. If you can just print out a megaphone silhouette, you can enlarge it and then create your own applique from it.
Edit 2: I found this die-cut applique resource. Have no idea if it would be cost-effective for you, but might be worth it:
https://www.appliquesquiltsandmore.c...ppliques-14980