Try insubuy.com. for insurance any little issue is a big issue so it’s not considered usual. So be prepared that your Dads premium might be higher than mom’s

to my knowledge, travel insurance doesn't cover chronic disease and pre exiting health conditions, not even they cover EMS service which is around $1000 for 5 min hospital ride. basically worthless . carry insulin and other medications from Nepal . regardless of your immigration , insurance status they cannot decline emergency services. so, no insurance is the best insurance.