Oh my, it has been a couple of years since I bought from them, but at least they were brass. Have a look at fat daddy vapes, they have the elite SS/brass connectors now, a 't510 insert' and a box mod connector of this- if it fits your needs.
edit: use the center post from the madvapes 510's to have the center hole, that MUST be still brass, so that one can solder to it.