I'm not a big advocate of stealth :) I prefer not to be but it's not an option unfortunately in this case.
Complete the following sentence Stealth has developed or is developing .... that solves the problem of ..... for ......
When completed you should be able to identity venture capitalist firms who wish to and or have made investments in that space. Corporates are more problematic if your reasons for stealth are to avoid the industry they are in. Angels are also problematic we typically syndicate which raises more possibility of them doing due diligence where you might find your cover blown.
Hope this helps