I'm just copy and pasting my comment for you. :)

If you're willing to spend money but don't want to reduce available space due to limited slots this was what I bought to upgrade from having 2x 2Tb external hard drives.

Samsung T5 Portable SSD - 500GB - USB 3.1 External SSD (MU-PA500B/AM) https://www.amazon.com/dp/B073GZBT36/ref=cm_sw_r_cp_apa_i_1E8SCbJVJBRNQ

Considering it costs 100$ just for a 500Gb, I definitely wasn't about to buy a 2Tb. So instead I bought this too.

Silicon Power 4TB Rugged Portable External Hard Drive Armor A60, Shockproof USB 3.1 Gen 1 for PC, Mac, Xbox and PS4, Black https://www.amazon.com/dp/B07GFDRFSR/ref=cm_sw_r_cp_apa_i_qJ8SCb6H93SBR

For another 100$ I bought this 4Tb, for 30$ more you can buy 5Tb. Easily beats paying 350$ for a 2Tb SSD as long as you just put games that need the boost on the SSD and dump the rest on the regular external.