Most "sega genesis model 1" third party power bricks don't output enough amps. Most of the ones out there only output 850 ma but the model 1 genesis needs 1200 ma. I recently came across this:
This's the right power output and the right plug size. I bought one and I'll update this when it shows up.
Most "nes to famicom adapters" are terrible. Most of them have the nes cartridge face backwards and I've even found some that don't work right in the av famicom. This is the best one that money can buy:
The picture is wrong the actual product you get is black. The nes cartridge faces forwards and it works with all famicom hardware just fine. I own two of these myself and I highly recommend this adapter for playing nes games on any model famicom.