portable hard drive buying help

[3BluEyedBabi]

So my hard drive on my PC is almost full...I have like 3.5 Gb left and Backblaze keeps sending me alerts that I need to add more storage to my computer so it can efficiently back up everything.

I do have an old Toshiba 1 Tb hard drive, but it is full and I haven't used it in forever. So besides Toshiba, what brands can you recommend and where did you purchase it if it was online??