So I quickly jumped on the net to see if I could find an easy recipe for some kind of rice cake substitute or nasi himpit. I found out how easy it is to make actually.
Just cook 1 cup of rice in 4 cups of water in your standard rice cooker (make sure your rice cooker is set to the 'rice' setting and not the 'porridge' setting). When done, tip it out onto a baking tray and roughly mash it up with a fork. Then using the back of a spoon, evenly spread out and press the rice down in the tray. Leave it to cool then slice into cubes.
For more frangrant rice, you can put some pandan or screwpine leaves in the pot while cooking the rice.
Easy right? No need to buy DIY ketupat sachets from the store anymore.