How do you make stick pins for a sewing theme cake? I also what to make a sewing machine to put on the top. Any suggestions on how to make one out of rice krispies? Do I need to put supports in it?

Don't know about a sewing machine.

By stick pins do you mean the large pin w/(usually) a pearl head that is used to pin a corsage on?  For that I would make very slim pieces of fondant, paint them silver/gray and add white 'pearl' on one end.  

Maybe this can help with the sewing machine topper.

I'm not sure which model you are making ,the links are for the old singer sewing.

http://thefrostedcakencookie.blogspot.com/2009/08/tuesday-toppers-sewing-machine-cupcake.html

https://s-media-cache-ak0.pinimg.com/originals/48/b4/ab/48b4ab8551610d05a6338899001b4306.jpg

As far as supports for the topper, I use either a base made out of fondant/gumpaste for the topper to sit on. Or use wooden skewers/toothpicks that I insert into the bottom of the piece to secure it to the top of the cake.  You could also use Royal Icing or chocolate to attach the topper. The links show the topper made out of fondant, if you were making something larger then I would  use RKT  since fondant can be heavy.  RKT is lightweight so you can make a larger topper

I would print a picture of the sewing machine the size you want and use that as a template for the RKT topper. Mold the RKT to the shape of the machine, cover in modeling chocolate to smooth the bumpiness of the RKT then cover in fondant. Cut out the knobs and as many details as you want out of the fondant and attach. Use the picture as a guide to get all the pieces in proper proportions. Remember to insert the  the toothpick/skewer before the RKT hardens. Hope this is clear, any questions, lmk.

This is a polymer clay tutorial you can do in fondant. There is also a pattern of the machine (modern version).