Some Vintage Sewing Patterns Websites tell you to buy the pattern you like/love and offer you some advice on how to alter it. Altering pattern sizes is hard to do if you are a beginner sewer or haven't worked with vintage patterns. It is much easier to work with the correct style of pattern in the right measurements. Maybe you won't find a pattern that is exactly what you want when you start working with them, but once you know how to work with vintage patterns, then you can get the one you love, and make it work for you.
Here is a helpful guide to sewing pattern shopping for a 1950's sewing pattern from the Advance Pattern Company. Please also look at the handy dandy measurement chart below the pattern descriptions!