Elephant and Admiral (the same company) take Amex. They're reasonably cheap, although watch out if they try to take a renewal premium without your explicit authorisation after the first year. I had to get Amex to do a chargeback when this happened to me. Their renewal premiums are always uncompetitive, so you're better off switching between the two sister companies every year and becoming a new customer every time, which will get you a competitive premium.