After Market Nav Chip

Has anyone purchased the after market chips sold on Amazon or Ebay? They seem cheaper than the "dealer" chips. But I'm worried about the knock off chips not working.

2018 Mazda 3 GT Hatch
I got one from Amazon for my wife's new 3GT. Cost was $99 and was a genuine Mazda part and worked perfectly. It was a 2017 chip, so will need to get maps updated but you get 3 years of those free. I would go with a "fulfilled by Amazon" seller as that gives you more leverage if you have issues.