[Cdesja5]

I'm in Canada and if I want to buy something like "gas" with my Canadian credit card but in the US, I have to enter a zip code with the same numbers (in the same order) as the numbers in my postal code (no letters like A, B, C etc entered). The rest of the billing address often does not matter so you can use a random US address. Why not try that to see if it works in your Kobo account? You could in that case select US as your country. In case you're not familiar with zip codes, they have 5 digits.