I don't believe there were any aftermarket decals made for the Otter Pops cars. The only decals I ever saw were in the Ed McCulloch Revell kit.
Slixx made Safety Safari Decals many years ago. They had all of the old Winston Drag Racing logos, etc. I haven't seen any for sale in quite a while.
I've never seen any aftermarket decals for the Jolly Rancher Top Fuelers. Only ones made were in the Revell kit from the early 90's.