You can go to subscriberstar and pay for it. Or you can go to dlsite (it’s not the best option due to how hard the payment is)
An easy get around is to use the dlsite points system, you pay on a website like 'for books' for a gift card, the only way I found to access it is through dlsite-> points-> purchase points -> purchase with card, it's still a bit of a chore but less of a chore then using other methods and been using this to get the works, as 1 point is 1 yen, but do be aware of like transfer fees cause you're still buying using yen, but it's only a few $ or £ or €. Dunno if this'll help but it's my preferred way to buy stuff from dlsite without having any issues so far.