I actually ran into this when I was in Germany last year. You can use CashtoCode at a bunch of international partner sites, not just in your home country. The CashtoCode casinos in Australia gives a rundown of which countries and websites are supported. I ended up using a voucher for a gaming site based in the UK while I was traveling and had no problems. Just double-check the website you’re using accepts it for your region, but otherwise, it’s pretty flexible.