I've saw a pretty similar script to that of TemplateMonster and probably the closest you'll come to their script since it'd be a custom one. I haven't used it before but from their demo on the site it looks pretty nice. It's called Template Seller Pro by AlstraSoft and can be found at http://www.alstrasoft.com

I'm not affiliated with them in anyway, I just came across their site when I was on the hunt for scripts awhile back through Google.

Hope this helps! *<|