this is for Charlotte...
Charlotte, I tried to PM you but your box is full and I can't reply to your question, so I will post it here... though I don't have a very helpful answer I wanted to respond to you all the same...
I am not quite sure of the availability of replacement parts in Canada, here stove top espresso maker is a very popular everyday item, we bought ours from a street vendor for 6€ (like 8 or 9 CAD), and replacement parts like the rings are readily available at kitchen/hardware shops.
Unfortunately I am not at all familiar with how the circumstances are in Canada when it comes to this type of coffee makers, but you may want to inquire about it at a large, well equiped shops of this sort, or a coffee specialty shop, or check on ebay(the only problem with ebay for something like this though, you may have to pay more for S/H than the item itself!).
I hope you will be able to find it, but if you can't let me know... if you could tell me the exact design or demention, I may be able to get it for you here.