Is there a workaround for Comparable Companies on niche, private companies?

I am currently interning at an MM IB firm in Asia, and have been tasked with coming up with the Peer Group on a client, who provides a single, niche service - and this particular service tends to be one of the multiple services that larger, public companies provide.

Hence, it is difficult to classify these larger companies as comparable enough companies.

This is not my first time running into this issue, in a previous internship I was also tasked with coming up with a Peer Group on another private company providing a single, niche service - unfortunately I got taken off the task as I had to help with other more pressing issues, so I wasn’t too clear on how my colleagues found a workaround.

I was wondering if it is possible to weight any metrics on a revenue-segmented basis, or if there would be any creative ways to go around this issue.

Thanks in advance!