So as somebody potentially getting into indie publishing, how would I find such people? How would I vet them?
The easiest way is if you have a community of various cultures near you. For example, someone who lives in New York City has an abundance of various cultures around the area, many with individuals who will be more than willing to talk to you and even critique any views or writings you may have.
HOWEVER, in this style of doing things, it MAY NOT reflect the attitudes of RPG gamers, especially white gamers. I had a project with the input of manyAsian-Americans and those from Japanese and Chinese cultures. Their ideas and statements HIGHLY differ from things I have heard on EN world, which had most of their ideas based off of a solitary RPG gamer who criticized certain RPG products. The cultural reviewers I had would not have agreed upon the points to focus on regarding cultural sensitivity by many of the things stated by that individual (who ironically himself is an Asian-Canadian I believe) and others in the RPG gaming community, but as I saw from a thread, there was still understanding by many of their viewpoints as well and one could even see a confluence of both of their sensitivity issues regarding their cultures if one looked for it.
On the otherhand, there were many things they brought up that WERE offensive that have been ignored by many of those who supposedly are looking at the cultures of Asia in relation to Western Perception.
What I'm trying to say is that what is culturally important in the broader sense out there and what they would tailor something in accordance with their culture in general may not be reflected by RPG gaming culture currently, and what is offensive or derogatory to the culture in general may not be seen as such by RPG gaming culture and vice versa. In addition, what they may find good or a great PR item for the general culture may not be seen as such by the RPG gaming culture and vice versa as well...
Which means in a general context, writing in this way for a more general audience and getting cultural readers that way may be good for more general writing, but may not be as good for RPG writing (noted from personal experience).
That said, another way (but more expensive) is to contact various groups that represent specific cultures you wish to write about. They DO charge more. Several of these groups are politically active (this as much as I can really talk about them in context of forum rules) and promote for rights, equality, and justice for the various cultures that they are a part of. They normally have individuals and groups of individuals that will be MORE than happy to review a product or read through it checking for sensitivity items. Many of them will enthusiastically support the idea of you coming to them, but in many instances they will charge for doing this as their time is valuable.
Once again though, expect that their opinions may not be the same as that of the RPG gaming community as it seems the RPG gaming culture tends to focus on different points of sensitivity than the general culture of various groups. There are some items which are focused stronger on by the general society of certain cultures than what is seen in RPG gamers, and vice versa...with RPG gamers being more conservative or liberal regarding certain topics.
In that note, someone suggested FB or other avenues to get sensitivity readers for certain subjects. If for a cultural aspect, I would suggest ensuring that they are actually part of that culture through some sort of verification (not sure how) to verify that they are, in fact, part of that culture. Some of this may be easy with certain cultures, harder with others. Another thing is if to get a more collective opinion. One individual may have specific opinions that are outliers and do NOT actually represent what the rest of their culture feels or thinks or believe or acts. There may be different parts of a culture that disagree of various points of ideas and may even have controversy between how they feel about different points of contention within those groups.
It may seem simple if one only gets one sensitivity reader, but it may be a more complex issue than simply one sensitivity reader may seem to indicate. Furthermore, what may be seen as an acceptable representation of a culture by an RPG may actually be HIGHLY offensive to many in that culture in a general sense, or at the same time it could be seen that their representation is highly offensive to RPG gamers.
I think it is actually a trickier line to balance on than it initially appears.