I have a copy of Star Odyssey for sale, gem mint and played only for five minutes.
I put the insert, manual and cart in a spare minty official Japanese Megadrive hard plastic clam shell case which it all fits perfectly in.
The reason for this is because when my copy arrived the cart holder tabs on the original case were broken off. Was not a really big deal to me though as I am not a fan of the Super Fighter Team cases as the plastic used is a bit flimsy and the outer clear plastic holding the insert is not textured like official cases are so it's very scratch prone.
Shoot me your offers, I will likely sell the game to the highest bidder if the price seems reasonable enough to me. Anything too low IE: The retail price of $50 or so that I bought it for, and I'd probably rather just keep it, as I will likely never find it again for sale once I sell it.
To be honest, to make it worth while I am looking for something at least in the 100 dollar range as the USD is very weak for me here in Japan at present times! But don't be shy to send me a PM.
I have a ton of seller feedback on the Neo-Geo forums under the name "Neo Maikeru". Paypal is the only type of payment I can accept.
Thanks for your interest.