Farsight, knowing your source is incredibly difficult these days, Luna being what it is, has killed most of the old ways of buying stuff.
The only people who sell person to person are scammers and spammers in Luna bank now.
That is the problem which needs to be overcome. There are people who prefer to do their selling face to face, and that is what makes the UP black market event so successful every month. I won't vouch for everyone who sells things at the market, but I do believe that most of the sellers are reliable.
There are also more than a few people in the alliance which we're both members of who hunt for high end products who avoid the sorts of people/groups who cheat. Those people are also good sources of gear.
It involves more work to get to know your suppliers, but in the end, I think it's worth it.