"niche firm" is a correct and usable phrase in written English.
You can use it to refer to a business that specializes in a particular type of service or product within a larger market. For example, "The company is a niche firm that specializes in custom web design."
When he joined, as an associate, in 1977, LeBoeuf was a niche firm, focussing on utilities, energy, and insurance clients.
Another niche firm, Clark Tracks, which makes caterpillar tracks for forestry vehicles, sells 90% of its products to Europe.
Neuberger Berman, a niche firm that focuses on value investing, was founded in 1939 by Roy Neuberger.
It would be unwise to set your heart on finding a role in a small niche firm staffed by just a few lawyers.
Morgan Joseph positions itself as a niche firm, aiming to provide research and investment banking services to small growth companies with market valuations of less than $1 billion.
Hunt, who was employed by the sports management giant I.M.G. before starting a niche firm several years ago, was a first-time visitor to Augusta National, appearing as McIlroy's guest.
These are niche firms, but all strong in their niches: ARM dominates its world market; CSR is a giant in Bluetooth.
There will be a place for niche firms, particularly in the small-scale generation market.
Yet they are not sufficiently focused to compete effectively against niche firms with geographic or technical specialities.
While those prime contractors all worked systematically with smaller niche firms to meet production quotas, the relationships would hardly be described as informal or collaborative.
French industry has no answer to Germany's Mittelstand, the niche firms that make high-quality capital goods and can charge premium prices for them.
