Looking for a push on barb at one end, and a threaded connector at the
other.

Most of the places I've found have been either trade suppliers or us
sites recommending places like Home Depot.

I'm looking at connecting 6mm silicon vacuum hose to a barbed connector
to be screwed into a brass or aluminium T-piece.

Also looking for a source of small coil springs that would fit inside
the T piece too.

Plan is to assemble a small manual boost controller for a turbo car
application, using a knurled allan cap bolt and locknut to adjust the
boost.
--
"Sorry Sir, the meatballs are Orf"
The poster formerly known as Skodapilot.
http://www.bouncing-czechs.com