A quick google search found this -
http://www.edwardsegalinc.com/index.cfm?Level=3&PG=3&PID=38&CFID=67011902&CFTOKEN=16254195
Youtube video -
[video=youtube;2h9bdh4udZ8]https://www.youtube.com/watch?v=2h9bdh4udZ8[/video]
I'd say it depends on what your grommeting. We use a pnemuatic machine for grommeting... really easy and quick. The above might be ok for banners / etc... but thicker material, I don't know how well it'd do. And it seems a little slow, for 20k grommets... but if you want portable, that might be the only choice. If you have air hoses throughout your warehouse....
[video=youtube;gWRVN9XqmWQ]https://www.youtube.com/watch?v=gWRVN9XqmWQ[/video]
Not sure how light that one is. But it looks pretty portable, even has a handle.
Not sure on the quality of these either. We have a big grommet machine that we just step on the pedal and it'll grommet. And even with that, I think I'd go crazy with 20k grommets...