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I doubt the multi carts have an sd card slot. The Chinese everdrive clones are cheaper than official but they aren't that cheap.

I got a decent quality Chinese NES multi cart recently it has over...

Everdrive MD and some Chinese clones.

Edit:
I think everdrive can run sms and some other stuff, I'm not sure and can't recall details now.

Sometimes it can be hard to find what you're looking for there, I've spent ages looking for stuff myself. I don't think the search function is very intelligent.

Edit:
I don't know anything about...

If you want cheap parts have you looked on aliexpress?