Thanks again for all the suggestions. I did want to give an update that getting them from a bank may also not be an option. At least it wasn't for the 3 banks that I've stood in line to ask (Citibank, BBVA Frances, Ciudad Nacional). I had still wanted to get the coins for the washer/dryers in the apartment building where I'm staying, but I've given up and will just have someone else do the laundry for me. Still pursuing the sube card and hope to get that soon.
My landlord did tell me that even if the banks did have coins, they would likely only give me 10 at a time. This would explain why stores don't have them either: there just aren't many to be had.