models

How many? Is Weight a factor? Why not just buy some plastic bar stock (delrin would be good) and have a competent machine shop with a CNC lathe make them for you? They can tap it then you can buy some all thread, saw it to length and screw it in. You will spend much more and waste a lot of time casting them with resin in plaster molds.

I am afraid your solution wou;ld cost more that buying already made steel couplings at $20.00. Since I will need several hundred I need it cheap.

Try an "Arts & Craft" store and by a bag of large plastic beads then for each one, heat the bolt enough that it can melt the plastic and stick the bolt in the bead.

Yes I think that would be the best, I do not live near an Arts & Crafts store but I will look one up. I have a small machine shop so I can drill the hole and use resin to glue it in place. The trailer coupler is the big problem. I have a 20 ton press if I new of a formable plastic I might be able to form a replica.

How about the white puffy stuff students used to make planets for in a science fair??

MidniteFighter

Check Make Magazine, Makezine.com . Issue 19 has a project in the center on vaccuum forming in the home oven. You might even be able to make them nest together to save storage space. Also using your press get thin flashing aluminum to press around a steel form.

The balls are not the big problem I just added that because it is part of the display. I need the information on reproducing the coupler more, One reply was to make one by CNC, I could buy the real thing for that price. I need something around $3.00.

Couplers could be made by vacuum forming a thermoplastic blank cut-out that has been preheated in an oven, popped into the mold and the vacuum applied from pump or a simple foot operated cylinder.

There was a toy system of a similar nature but used thin plastic and stock mold shapes.

Another place to check would be a ceramics/pottery shop that makes its own greenware. They may be able to help you make a simple mold. As you have a machine shop, you could make the prototype out of wood and form the mold around it. As I've never done this myself, I could just be blowin' smoke out my you-know-what, but I have several friends and a sister-in-law who are experts doing stuff like this, and I've watched them work. You might make the items out of plaster or some other moldable compound besides the kind used in ceramics shops, but this is one place that'd know how to make molds.
Also google "greenware" "ceramics" and so forth and see what turns up.

Good luck!