Any USB-C mobile SSD hard drive should work well. $200 should get a 1TB. Any brand is fine: Samsung, G-Technology, Western Digital, San Disk, LaCie, Other World Computing.
You'll want to make sure that whatever capacity you pick is a good fit for how much data you have in a typical project.
You could add a larger, standard USBC (like a 5TB USB-C mobile drive or 8TB to 12TB USB-C desktop drive) to copy project folders over to once completed.
Of course, then there are backup considerations.
When editing my own projects, I like to create a folder for each project. At the very minimum, there are three folders inside the folder for the project: Exports, Premiere Pro Project Files, and Source Footage), Set the Scratch Disk to "Same as Project" and make sure any footage you import into a project is in the corresponding folder prior to doing so.