First of all: This is a Chinese fan-made project. Not official merchandise, not genuine game, just for fun.
Here is what happened. I seemingly got the NS2 launch title Pokémon Emerald for only $14. The seller said he had exclusive access, and even claimed his friend worked on manufacturing NS2 game cartridges.

He sounded really confident. I thought if I could get this for $14, posting it online would blow up. He told me this was top secret, do not share it publicly, and he would send me more updates later.
Three days later I got the package. What was inside was nothing like what I expected. I thought the NS2 Pokémon Emerald box looked a little small… And it works perfectly on 20-year-old GBA and DS consoles! I get it now. Nintendo wants old players to enjoy this game. I want to ask everyone, did I get scammed?
The big reveal
Actually, I had a buddy in the modding community build this for me at cost (total $14): The cart is based on the open-source Chis Flash PCB with RTC support (cost $11, playing this romhack while waiting for my authentic copy to arrive), and I added a standard blank GBA cart ($3) just to round out the order. Let's keep it on the down-low—he only charged me for the pure hardware and DIY labor, this is absolutely NOT some scalper flipping roms for profit.

Box: A fan-made NS2-style GBA storage case from another shop. I originally planned to buy a normal case and found this by accident. The maker likes NS2 cartridge boxes and is a veteran GBA player, so he made this custom case. It uses a tape-style outer shell + 3D printed PLA inner tray + custom high-res cover art. Single unit costs $3.5, discount if you buy three. I also pretended I own GBA Dragon Ball: Advanced Adventure and Castlevania: Aria of Sorrow. Genuine physical copies of these three GBA games are very expensive right now. These are great for personal play!

Disclaimer: My friend only charged for the bare PCB hardware. Theoretically, you can put any GBA game into this shell and flashcart.
Lastly, for hardware mod fans, I share a comparison picture of chips used on different homemade GBA cartridges. What is fully integrated hard-packaged chip? What is COB soft-packaged "cow dung chip"? You can see the difference clearly. Decide yourself if it is for collection or casual play.


Quick info: Chis Flash is a well-known open-source GBA flash cart project from the Chinese homebrew community. People can order PCBs and solder it themselves. It focuses on RTC and low cost.