Has anyone been able to create an item label template with a bar code based on a custom field?

Yea you can do this with a saved search template and url parameters. I got it from a blog somewhere, if you Google it you'll find it.

interesting. I have a similar requirement. I was able to find it here https://jcurvesolutions1.zendesk.com/hc/en-us/articles/360000219223-How-to-Print-Barcodes-from-Item-Record-using-an-Advanced-PDF-HTML-Template