How to set width of dropdown content so consistent

How can I set the ComboBox dropdown width so it does not keep changing on me based on the size per page dropdown page? What I really want is for it to be the width of the longest “caption” in the entire dropdown value list. I have been exploring using v-filterselect-suggestmenu and width: 50em, but that gets overriden with awidth: auto. I am hoping there is some CSS trick I don’t know.