Pale Rider
Veteran
I would imagine that convictions etc would provide a reasonable starting point.
Still quite difficult to gather in one place, as I understand it.
Ethnicity may not be recorded with the conviction, so even if you got the list you'd be stuck with 'his name sounds white' or 'sounds Asian'.
It's also been officially accepted some police forces didn't go after Asian gangs out of a mis-placed sense of political correctness, which means convictions are not a reliable source, albeit better than nothing.