Where could I get a Nintendo 64 expansion pack?

[DonCaballero]

I know I can get them online but I want to know if there is some physical store or something that might have them.

 

[Powdercake]

You might be able to find a used one at a GameStop or a garage sale. However, no retail store is going to stock them nowadays (they're what, over 12 years old?) so your only other option is going to be online or at video game conventions.