Open your VPN add a game to your steam shopping cart, than you can change your country / region at cart page temporarilyGerman here so I had to deal with this shit already and can add 2 things:
Steam keys will work even if you can't access the game's Steam page (unless you bought a key for the wrong region). But you obviously have to buy it somewhere else. Like a reseller, but I doubt this game will show up on one of those in the near future.
Second thing, VPN won't help, your Steam account is linked to a country and that's what decides if you have to deal with this bullshit or not. And it's not that easy to change the country.