I found a plug-in for this "problem". To be exactly it's not a true workaround. It's just a web site offering free video conferences, that made a plug-in for Pidgin. That means the site works on any system!
The only problem with it is the following:
It only is available for Pidgin running on Windows!
The setup that can be downloaded needs a standard Pidgin installation. (Wait for the workaround!)
Workaround:
It doesn't matter if Pidgin ist running or not!
To prevent to have a standard installation, just download the executable from their site. Hopefully you got 7-ZIP on your portable device or host PC. Open up 7-ZIP and open the executable internally. There you will have only 1 folder. Go into that folder and extract the only file in there (MeBeamPlugin.dll) to "%PortableApps%\PidginPortable\App\Pidgin\plugins\". Done!
From now on, follow the instructions not missing step 1 on the MeBeam site starting at step 5:
http://blog.mebeam.com/2008/07/pidgin-using-me.html
Have fun with it!