How about a minature force field so you can put it anywhere you want with no fuss or muss? Oh shoot I forgot it is only 2005. So what is wrong with a rad box?
its hard to compromise between portabillity and having a external wc set up. My recomendation, buy a 1 X 120 Rad, there are a ton of ways you can set those up in cases internally. BTW I wouldn't travel with a wc set up unless you check that system ALLL of the time... its not fun trust me.
Ok... so you don't want to mount it on the outside because you ship your case around a lot. So then why don't you mod a bit and mount it on the inside like I had suggested?