I haven't seen such a thing... I assume you want to tuck it into a shirt, so there wouldn't be much on view. Should be a simple matter to /cobble something together/ lovingly craft a detailed model. :) Did you have a shirt in mind already? And yes, a reference picture would be good, since there seems to be a good deal of variation in styles. See, for example:

en.wikipedia.org/wiki/Cravat
www.tomsawyerwaistcoats.co.uk/subprod/how-to-tie-a-cravat-0001283.aspx

• which just happen to be the top non-sponsored search results on Google.