1tb external USB3 SSDs have come down in price.
2tb may be available, but of course will cost more.
You can either buy an "all-built and ready-to-go" drive like the Samsung t5 or Sandisk Extreme (there are others as well),
or
You could buy a "bare" 2.5" SSD and the enclosure of your choice, and make your own (which is what I do).
If money is no object, there are also external thunderbolt3 SSDs, such as the Samsung X5, but they are PRICEY for the larger sizes.