The carts. The stickers on the carts. The inserts. The manuals. The boxes themselves all needed to be created perfectly by dimensions of which match other Gameboy games. After finding some good people to work with I ended up printing 100 complete in box copies of my game.
I've been looking into this and finding the manufacturers is the stumbling block, particularly for the boxes. With Alibaba finding cartridges to dump to is slightly easier, though I'm very curious the route you went!
It was quite expensive and I, as most developers, am quite broke. It came as a surprise that all 100 copies of the game sold out in 1 day and I was absolutely baffled. I still am. The support that I have received and continue to receive has inspired me to greater heights and I cannot thank the community enough for showing me that I CAN do this. I can follow my dreams of being a game developer. I CAN make a game. I CAN make physicals and guess what?!?! SO CAN YOU! If I can do it, so can you.
That's amazing and so encouraging! I absolutely love this resurgence in GB stuff recently. :D
BTW- Fun game, I very much enjoyed it and looking forward to getting a physical copy soon!