Since the only other post I can find on all of reddit that mentions Oshi sushi is a photo from 2 years ago, here's a few links for the next person:
This is the mold/press I'm thinking about buying. Amazon has cheaper ones of plastic or pine, but I like the look of this traditional cypress press. http://www.amazon.com/Kotobuki-Oshizushi-Wood-Rectangular-Sushi/dp/B00462R8TO/ref=sr_1_1?ie=UTF8&qid=1424355865&sr=8-1&keywords=oshi+sushi+press
Here's a site with some basic tips and a couple of nice-looking recipes: http://www.allaboutsushiguide.com/oshi-sushi-recipe.html
Here's a super-simple version using a milk carton: http://www.annathered.com/2011/06/19/how-to-make-oshi-zushi-with-smoked-salmon/
I think it looks fun to make and would be a good option for my daughter and other guests who turn their noses up at seaweed.