https://bgp.he.net compass, globe, etc
I've said before there needs to be a community project to determine where relays *are not* and then work its way through them in attempts to place there.
Just as you can "get bridges", prospective operators should be able to "get hoster/isp/vps/country" and then go knocking on those doors.
And annotate it all in a db / wiki, revisit them, etc.