Is there a way that I can make my used/broken soft plastics into new ones without a mold?

Superglue

I meant after I melt it down.

You can make molds pretty inexpensively using Bondo. There's information all over on the topic if you google it. You are better off using baits that have one flat side, like a jig trailer for example. 

 

Also, if you are remelting, get yourself some heat stabilizer or you run the risk of having burnt baits.

Bondo you say.....

When I was much younger- and molds were hard to come by- I took a Slug go and put it flat side down in a plastic container. I poured resin that I found in the auto section over the worm. When it hardened I removed it from the Tupperware, pulled the worm out, and had a mold. It wasn't pretty, but it made a lot of baits.