Have you looked at the following:http://www.okwenclosures.com/index.htmhttp://www.polycase.com/http://www.boxenclosures.com/
All three have a wide range of enclosures available and you might find something that you like better than a standard potting box or square enclosure. They have a lot of handheld options that come with battery compartments as well which is a huge plus.
All three of these sell low volume, even single units. I have enclosures from all three and I like OKW the best but they are all great. I thought the fabrication on the box enclosure one wasn't quite up to par with the other two.
They all provide customization services but I don't know the minimums. I actually just sent an email to OKW asking about screen printing minimums. I have access to a CNC to cut holes/openings. Yeah Me! More than likely there is a bulky setup charge regardless of qty. So if you want 1, you may have to pay a $500 setup plus $1.00 for the part. So if you do 100, is it worth an extra $5 each to have them cut perfect? I would say yes but I don't know their setup costs. I am basing this off of what seems to be common practice.
Look up your local machine shops. Most of them will work with plastic. Many people just assume that they only handle metal. Anyone with a CNC can set you straight and it won't be overly expensive. They can probably even set it up for you if you don't have access to the file type they need, probably solid works or autocad. If your project is really cool and you can get them interested, they might even do it cheaper.
Edit: Just realized you are in Israel. I was going to suggest that you ship them direct to me and I will cut them and forward them to you. A little challenging from here to there.