I have two Rational DRO's I purchased on AliExpress. I purchase the first for my mill and liked it enough to purchase a second for my lathe. I chose the same brand so the Head units (2 axis vs 3 axis) would have the same interfaces.
There are many other brands available on Aliexpress. No complaints about the sellers, though I did make sure they had 98%+ ratings on reviews. Each was purchased from a different seller, as each had better deals on 3 axis vs 2 axis units. AliExpress acts as an escrow agent and will not release your funds to the seller, until you acknowledge receipt and no issues with the order, or you don't respond with and issue within 21 or 30 days {I don't remember) after receipt.
In my case there were no issues, so I just acknowledged receipt was ok, so the seller could get paid.
If you do purchase from Aliexpress, make sure you communicate clearly with the seller what you want, using the question feature, as it gets logged incase there is a dispute.
Also research what you are interested in so you can understand what resolution scales are included. In my case, the "Packaged" deals listed in the sellers sites had the lowest resolution glass scales. Looking at Ratioinal's website I found the scale model number with the resolution I wanted. I then communicated with the seller what the price would be to upgrade the scales to the model I wanted. Once we agreed to a price, I placed the order.
Hope this helped.