Here's a link to Pet Plan Insurance. I just signed up with them. They seem to have the best coverage available, and I've done lots of research. You aren't going to find any insurance that will cover "pre-existing" conditions, but this one will continue to cover issues that arise after enrolling, for your pet's whole life where most other companies won't. There also isn't any limits per condition or hereditary/congenital exclusions. And they are reasonable.
And unlike all of the other Pet Insurance companies I researched, Pet Plan does not have a benefit pay-out schedule. They simply re-imburse for any/all treatments for any injury or illness.
You can choose $50/$100/$200 deductible with 0% coinsurance. That means 100% coverage after your deductible. And the basic plan, Bronze, pays up to $8,000 in re-imbursements per year!