Now you could just take a knife, cut it in half and stick it into his hand, but why break a knife and prevent future use for it. For reference I used the Deathstroke Arrow series leg knife for reference and began by gluing 3 this pieces of plastic sheet taken from a mezco box and cut out the top knife shape and the bottom pummel or base of knife.
To get that nice knife shape I took scissiors and files to 'sharpen' the knife and by this I mean give the appearance of a sharpened knife not actually sharp
for this I took 2 bits of plastic sheet, cut a line hole through them and glued together and then shaped into and oval. Then I just slid it over the blade and glued
So here after coating the dried apoxy in glue for strength I painted it black, then Painted a second coat with dark silver for the blade and a bright silver lining on the 'sharpened' part
As you can see Joker now feels more complete. You could use this method to give him stain glass shard knives like he uses at the end of the game by making only the blade and using a sharpie to colour transparent red, or better yet use red clear plastic
Disclaimer
Customize at your own risk!
Customizing can be a fun, but dangerous hobby. These tutorials are contributed by other customizers. Some of the things recommended in the tutorials may be dangerous, such as the use of boiling water or sharp objects. You shouldn't attempt anything mentioned without adult permission and supervision. Figure Realm and/or the authors of the tutorials are not liable for any injuries or damages occurring from any attempt to follow suggestions in these tutorials.