This handmade custom Super Mario belt, depicting the final level, was apparently created by Etsy seller SalukiFeathers, though the belt is not actually available through that store. The corresponding Reddit thread is kind of a mess, with the poster claiming that the belt was made as a Christmas gift for himself and/or his brother, by his sister, and so forth. Nevertheless, this definitely falls into the category of "awesome nerdcraft," and also, "shut up and take my money."

Super Mario Leather Belt with the exact layout of the final level in the original Super Mario :) (imgur.com) (via Reddit)