It will depend on their age, length of stay etc.
If they are from the UK my article article on travel insurance may help.
Towards the end of the article are links to travel insurance providers for the over 65s, or those with medical conditions.
For those under 65 (and possibly over) there is a link to an insurance price comparison site that does NOT require you to provide your email address and details before you use it. http://inblighty.com/trekbooks/trekinsur...