Travel

I’m not in my home country, therefore I can’t buy the usual before departure type of medical insurance.

I know that I can buy travel insurance through Japan National Tourism Organization after I arrive Japan.
https://www.jnto.go.jp/emergency/eng/do_travel_insurance02.html

But I can’t access the website from outside Japan. Does anyone know if I can increase the maximum coverage ( say about 100 millon yen)?

Besides, are there any good insurance companies offer high coverage travel medical insurance for tourist?

Thank you.