My name is Sam.And i would like to do the rasberry pi portable project but I don't have a 3d printer can you sell the case. 
I am sure if you contact a fabrication service in your local area they should be able to 3d print/Laser cut a case for you, in that case you would need the appropriate files.
If you want a 3D printer for a low price, try the Printrbot Simple, a cheap but high quality printer.
Not many people may wish to sell you a case for many reasons, so check out services in your area.
If this helped you, then mark your question as answered and leave a like 
thanks but im 11
You also make a the pi case with wood and ask someone to help
Sam, are you in the UK?
If so, I could probably supply you with a 3D printed rear case. But you also really need a laser etched front panel. I can't do that. Does anyone know who could do laser etching?
srayner
Sorry I'm not.
You may also want to see if there is a Makerspace in your area and pay them a visit. I am sure the folks there would be willing to help out. There is a directory of Makerspaces at http://makerspace.com/makerspace-directory.
This is a cool project that my son is interested in making. We are just getting started with it so I am trying to see if Ben or anyone else has posted a parts list, print, and cut files for this.
Sam, I hope you are able to get some help and build this. I think this is a great way to get young people interested in the maker community. My son loves playing video games and I try to get him to do some creative things. This project is perfect to get him to learn some Linux, hardware, and programming skills. Once he has MAME setup and plays it for a while I am hoping that he will start to write his own games in Python and maybe C++ a bit later on. One can hope.
Good Luck and Have Fun!
I found the information on Thingiverse. Raspberry Pi Portable by benheck - Thingiverse