You are going to have to do something.  Do they take the regular 1/8 pins.  If so you can get 50 from Do-It really cheap.  If not then you will have to make them yourself.

Home made ones can be out of wood as well as metal.  I use regular house romex for my small pins because I had it on hand and didn't want to drive all over the place looking for the right size dowell rod.

If you have romex a bit too small you can put a piece of duct tape across the pin slot to hold them in place.  Good luck.  If you need more info.  Post up.

Try them.  I never had the right size.  You would have to cut the head off for sure so the mold would close.

What size fg do these molds take?

I'd buy a bunch of pins.  You will need them for painting and molding.  I'd buy atleast 25 of them.