@FernieS from experience, a different one would work. (unless it has a voice component to it) So, if it is just data, it should be good
again, if a different one does not work, support can help to sort it out. So, you won't loss them by trying a different one first if you need one in a hurry.
@FernieS - you can add a different addon 'bucket', so not the same one you purchased and are using now.
OR, you can ask CSA to add the same one for you. Not sure if there would be an issue, once your first one runs out though. You could ask. CSA contact methods also found here in Help Articles for future reference:https://www.publicmobile.ca/en/on/get-help/articles/contact-an-agent
@FernieS you have to buy a DIFFERENT roaming addon if you want to have it immediately without support's help.
If you need the same one that is not expired yet, you will need support's help to re-buy the exact same addon. In this case, please message support and they can help. Message them here: