I'd do one of two things (or both).
1. I'd contact the manufacturer, online or via phone or email. Most packages or sites have a "contact us" link.
2. I'd guesstimate, based on the individual components. i.e., 5 oz chicken, 2 oz carrots, 3 tbs alfredo sauce, etc. Livestrong can give you good generic calorie counts for sauces, etc., if you can't find them on spark.
I use option #2 when I'm at restaurants, and it has been close enough. Remember, you can't make "perfect" the enemy of "good." Go with "good" and know that over time it will probably average out.
Kay -- Dallas, TX
Lower Body Lift 12/12/2012
Maintenance as of 1/1/2013
| current weight: 25.0 over