Hello,
pcengine is one of my favorite retro systems and I like to learn new stuff of it. I discovered Neoflash created a 128M pcengine flash cart.
Neoflash is better known for their GBA and NDS flash carts, but they are now starting in the retro world too. All their carts use only USB instead parallel like other competitors, having a lot faster transfer rates and better compatibility in newer computers.
Their pcengine flash cart was released since april and even has a box a label. It has a proffesional looking and there are 64MB and 128MB versions.
A this moment there are no other offers until now for a review, so it's quite possible they accept your offer.
Go to here and write a forum thread about your review offer, they will finally accept or not after judging your page. Please mention me in the forum post 
Best regards,
timofonic
PS: I'm not from neoflash staff, just an enthusiast about the retro scene and flash carts. I did some PR about uCON64 too (find my nickname here).