I'd personally have gone with a mix of milk and single cream. I guess, but really can't tell you because I've never been to America, that half 'n' half which has already been suggested to you, would be a good place to start. However, I'm not you. I don't know what you like and I don't know what is wrong with the milk you presumably use ? So it is impossible for me to say anything other than start with milk and just make it more creamy until you get to the point where you like it and remember that milk (and all dairy) isn't actually that good for you and that unless you are seriously active, as in a farmer or cycling around the world (which I've attempted), those levels of fat and calories will have a long term impact on your health and not a good one.
Have you considered a healthier alternative of yoghurt? (Unsweetened yoghurt, not low fat, just normal full fat but unsweetened).