Learning to model yourself is a good option, but it is not quick or easy, nor will your initial attempts be of a high quality. Unfortunately, your options are either to teach yourself, or to use character generation software. Alternatively, if you happen to have a pile of spare cash around, you can hire an artist. As an artist who also likes money, I wholeheartedly support the latter option!
Blender is a good starting place, like Gunner mentioned, and also has a wonderful community built around it which has supplied a wealth of tutorials. Even if you go down the daz/poser route, that knowledge will be indispensable, because something will go wrong, or you’ll need to make an asset or prop yourself.