My wife is the same, she loves the Chicken Korma you are talking about - very mild and more creamy than other curries. And we just ask usually if it is tomato based or you can tell from the description. I also make it at home using of those bottled sauces, which she likes as well. Here are the three we have tried and she likes the Sharwoods the best.

http://www.pataks.co.uk/products/kor...ing-sauce.aspx
http://www.seedsofchangefoods.com/ou...r_sauces&p=271
http://www.sharwoods.com/Indian/prod...king-sauce.cfm

You should be able to find these in major grocery stores, though not all three at the same time.