depending on how hot the soap is when you make the embeds, look for candy molds at places like BigLots, also for jello molds. Of course they would also have some at Michaels or even the Wilton area of Walmart.
Go out onto freecycle and post asking for jello and candy molds. I know several people here who have done that and gotten tons of them each time they have asked. If I knew where mine were, I would pull out some duplicates and send them, but after moving and all, I haven't even got an idea where to start looking.
Another way to do this is to pour some soap into a shallow pan like a jelly roll pan or cookie sheet iwth sides. When it is cool enough to handle but not set, use cookie cutters to cut the shapes you want. It works pretty well. Or you can put a bunch of different cookie cutters in the pan and pour the soap into them and let them set up in the pan, then break it all apart and pop the shapes out of the cookie cutters. It also works with fudge. (I have done ti with both soap and fudge)
For a different soap item, get one of those long loofah sponges that looks like a cylinder. You can cut it into slices about 3/4 to 1 inch thick, put them in a pan and pour soap on them to make an exfoliater. You can also use a loaf pan and put the entire loofah in and then fill it with soap. When hardened you cut it into slices. You need a power saw to do that, and then some hot water to soften the edges to smooth it and make it look pretty, but they usually sell very well. Around here it adds another $2 or so to the cost of the bar of soap if it is packaged prettily and you have it all smooth looking.
Keep an eye out in the jello aisle at the store for when they have the molds. Also check Kraft's website because they sometimes have deals on them there too.