Yeah like I said in my first reply, Sex Screws.
They have a female sleeve with internal threads that the male threads screw into. You will only find them in the round type but you should be able to make them work.
Usually they are all metal. It looks like the originals have a plastic female part.
I know you are saying, "This guy wants me to walk into a hardware store and ask for SEX SCREWS". Yeah right and while i'm at it I'll ask for a left handed hammer, a Board Stretcher and a Sky Hook.
No really that is the industrial name for them. Do a google search.
The ones you have now, the originals, are captive. Meaning there is no screw driver
slot/philips on one end and they are held in place so they don't turn by the square section. The ones you will find have a slotted or philips bit head on both ends.