Hello,
I just googled "plastic canvas triangle shapes" into Google and found them online at Hobby Lobby. Here is the link:
http://www.hobbylobby.com/Yarn-Needle-Art/Needle-Arts/Plastic-Canvas/Triangle-Plastic-Canvas-Shapes/p/36506
I did not do a search for the diamond ones, but you would probably type in "plastic canvas diamond shapes" into Google to see what comes up?!
The manufacturer we go through doesn't make those types of shapes any longer so that is why we don't have them :( Hope this helps!
~Kristi @ EPC