grammar - Missing particle after など in article about new technologies to monitor employees

I'm reading this article about new technologies that are getting introduced to monitor employees.

I am unsure about the following sentence. I do not understand why there isn't a particle or something like it between the など and the 230. Is this a typo or what is intended here?

ソフトウェアをつくっている会社など２３０の会社が新しい技術を紹介しています

My Translation: 230 companies are introducing new technologies, where these companies and similar places are producing software

Answer

In Nominal apposition in Japanese (2004), Rumiko Sode calls this など an "exemplifier", and considers this construction a type of apposition in which one noun phrase restates a subset of another.

Basically, you've got two noun phrases next to each other:

N₁などN₂

Which expresses that N₁ is included within N₂. In other words, N₁ is a restatement of part of N₂. It could be translated in various ways depending on context. For example:

秋田犬など大型犬に最近人気がある。

Recently, Akitas and other large-breed dogs are becoming popular.

Here, 大型犬 includes 秋田犬 as a subset or an example, and the noun phrases are linked together by など. Nothing is missing between them.

Likewise, in your example:

ソフトウェアをつくっている会社など２３０の会社が新しい技術を紹介しています。

The larger set is ２３０の会社, and ソフトウェアをつくっている会社 is some subset of those 230 companies.