This wasn't my idea, but I don't recall where I originally saw it. I have had a vise which has been missing a handle for quite some time now. I finally got around to replacing it. I used black iron pipe from Home Depot and a rubber washer to keep it from slamming too loudly when the handle drops and the endcaps hit the vise.
https://drive.google.com/open?id=1jMDSwEpluN8ic4-wLltW2llRfpm_YnVu
https://drive.google.com/open?id=1jMDSwEpluN8ic4-wLltW2llRfpm_YnVu