I suggest cutting your losses and just get a Mega Drive based Everdrive when buying a flash cart for the Master System, since the Mega Drive supports SMS games anyway. Just expect to solder in your own pause button, unless you can get someone in Europe to do it for you.
Well, the SMS can play those OLD SG-1000 games. The MD can't (no video). There are a few of those I like playing, like Drol.
Honestly, I'd be just as happy with a good Genesis/MD -> USB adapter. I'm really just all about the input being authentic for the experience.