Its not as bad as all that. First, DO NOT let a few road blocks crush your spirit! Buck up! You're going to hit this block, and many more, but they are not really road blocks, just bumps and pot holes. You can get past them.
Finding an enclosure can be a difficult problem. I encourage people to find something readily available that is close to what they need and then design to fit it. If your volume is low, this is the way to go. There are companies that make generic enclosures. Start with:http://www.polycase.com
If you can't find something you can use, maybe because it needs a funny shape or something, you have to make a custom case. This can be pricy. Sometimes you need to use "injection molding" which means you need a mold made. That can be expensive, but then each case is very inexpensive. If you go with "no mold" technology, then people will essentially machine and glue plastic to make a case. There is still an upfront cost, but it is lower, but each case is then more expensive. Google "no mold case" and you'll find many companies that do this.
Hang in there and good luck!