Here's a link to the online catalog at MyNotions.com. The catalog web address differs from the direct access address here:

http://www.mynotions.com/index.asp

They have an assortment of separating zippers in many colors and lengths: 10, 14, 16, 18, 20, 22, 24, 25 inches.

The 10 or 12 inch size should be about right for an infant jacket.

HTH,
CMC

Here is a link that might be useful: separating (and other) zippers at mynotions.com

you also might consider snaps, they come is great pastels and bright colors , are a breeze to put on and you'll never have to try to zip a wriggling baby

Thanks! I measured and the length needed is 7 inches, so I may go with snaps or velcro. Thanks again.