What size do the tablets have to be out of curiosity.
You have silicone ice cube trays right up to muffin. How about old school flour and water glue?
Make solution, fill silicone with kitty sprinkles, add glue, leave for while.
They need to be about 13cm diameter I want a single charge to go in my MK2 wildstoves woodgas stove (it also serves to stop pellets falling through the holes in the bottom)
I've never had particularly good results with flour/water glue. It always ends up going mouldy in damp environments.