If you don’t mind to pay a bit extra for shipping then Amazon US. Amazon US has the Blu-ray that is the same as the one which is selling on Amazon JP

https://www.amazon.com/High-School-DxD-HERO-Blu-ray/dp/B07MCW81NS/ref=mp_s_a_1_1?dchild=1&keywords=high+school+dxd+hero&qid=1587603243&sr=8-1

It is the best to get it on Amazon Jp but you could also get it on US

https://www.amazon.com/High-School-DxD-HERO-Blu-ray/dp/B07MCW81NS/ref=mp_s_a_1_1?dchild=1&keywords=high+school+dxd+hero&qid=1587603243&sr=8-1

Here’s the same one that also one Amazon Jp