There's a company named Southern Bloomer Manufacturing Company that makes a variety of cleaning patches and muzzle loading patches.
Their .50 cleaning patches measure 2"X2" and come with 500/bag.
Their Universal Rifle-Pistol Cleaning Patches measure 2.5"X2.5" and come with 125/bag.
They also make 3"X3" shotgun patches and many other sizes.

http://southernbloomer.com/products.html

Southern Bloomer Mfg. Co.
1215 Fifth Street
Bristol, TN 37620

Phone: 423-878-6660