Hi Greg,
I think that companies such as Isis Dei have 'design' as their core competency, and would most probably not have their own manufacturing capabilities to produce their products; so they outsource the production to a firm that can make to Isis Dei's specs.
In all honesty, even though designed in the USA, these products are almost certainly manufactured in the Far East (China, Hong Kong, Taiwan...). In order to identify such manufacturers - you could use sites such as Alibaba.com, Made in China.com or other such sites. (I personally am not a big fan of such sites, as the effort needed to establish a relationship with the RIGHT (i.e. reliable, honest, able, etc) manufacturer is considerable. That said, I'm sure it works for some.
Another option is to partner with a sourcing company; they often have a network of manufacturers, and even if they don't - they can find one for you, based on the requirements you set. Some will be able to manage site visits for QA/QC, oversee the production and even the logisitics.
However, not all sourcing companies are equal and I've heard varying opinions about them.
Now, I apologise for the following (blatant) plug! I started up a sourcing company, HQ'd in London, with offices in Hong Kong & China since 2003. We manufacture & source a range of products, and manage every supply chain step (QA/QC, prototype production, payment management, packaging, logistics, UK customs clearance, Duty & VAT settlement, delivery etc) to get those products to you and make sure the final product is exactly as per your specs/designs.
In a nutshell: all the advantages of manufacturing in the Far East, without the pitfalls & disadvantages.
Apologies again for the self-promotion...