Softcore or hard? You could start by looking at Renderotica that has model morphs and accessories. You will need a base Daz model first (Genesis 8/9 etc.) and decide on the appearance you want.
A guy with a 20 inch shlong riding a shaved platypus wouldn't be safe for work. Kinda depends on what your fetish is doesn't it? Something odd like an 800 pound anamorphic hippo woman giving birth to a litter of goblin midgets?