I don't know if they carry the envelope stamp, but Repeat Impressions out of Freeport, Maine sells some great stamps. Check out:
www.repeatimpressions.com
The "Funny Bones" category has some great alternatives for "Made by" stamps - including:
"Rubber Stamps = $7000.
Supplies = $4500.
Handmade Card From Me = Priceless."
"This ain't no stinkin' off the rack card...I made it with my own bare hands!"
"What were you expecting? Hallmark?!"
On a different note, check out the Stampers Christmas Carols under the Stamping category and the new FLIP stamp sets.