My bars are around the same size as soap buddy's. I found these great silicone molds at Target that were meant for lasagna, but are way better for soap! There are two channels in mold and each channel holds approximately 2lbs. of soap. I have more than one of course!
They do make it kind of hard to cover in plastic wrap because there isn't a lot of clearance, but I put a plastic tub on top and a towel over that, and it works out great for me. I really like the fact that I don't have to burn through parchment paper with this mold. I use other mold for different things, but these are the ones I use most frequently.