I’ve looked through the following sets:
- Pokémon Rumble- Pokémon art contest cards
- Southern Island set
- Lucky Stadiums
- Blaine’s Quiz cards
- Tropical Present Jumbos- Radiant Collection part of the XY Generations set- Pokémon Pal City- Pokémon Fan Club
- Tropical Tidal Wave and Tropical Wind and Tropical Beach and Champions Festival
- Switch
- Japanese Jumbos
- Vending Series 3 Deck List cards
- My own collection
- etc.
and came across the following cards featuring Magikarp (excluding Magikarp cards themselves, and excluding the four already mentioned by you):
Art Academy Mew (good luck with that… 
)
1999 Tropical Present Jumbo Postcard (full artwork of the Southern Island Marill you already have):
A Golden Magikarp trophy is present on this Pikachu Jumbo card:
Also, I’m not entirely sure, but I think the fish in the Neo Genesis Super Rod is a Magikarp as well:
Oh, and of course the Magikarp Poncho-wearing Pikachu:
Greetz,
Quuador