It is hard to recommend any particular company, as everyone’s needs and standards are different. You could start by reading some of the information on types of coverage etc. provided by InsureMyTrip, which is a website we use, along with Squaremouth, to search and compare policies for “standard” trip insurance that covers both trip cancellation and medical insurance/evacuation.
https://www.insuremytrip.com/
The cost of the insurance depends on the cost of the trip, age of the travelers, length of the trip, and level of benefits chosen. Three of those things you cannot control, but the last you can, so try to get an idea of the amount of medical and evacuation coverage you want/need. And remember that the cost of your trip is only the non-refundable costs (like a RS tour, or other tour, or hotels you prepay and cannot cancel, maybe your flight costs if they are non-refundable and not-changeable. You do not need to insure the cost of hotels you can cancel up to a day or 2 in advance.
The website will produce a list of many policies you can compare for cost and coverage, and give a rating.