If you are still leaning towards wanting contacts for this cosplay, you might consider trying mini-sclera lenses. You said your eyes are smaller already, so these may be enough to work. Due to the size if mini-sclera lenses you might not find both the red and black combo design, but if you picked solid black, that still gives the creepy effect. Or if you chose solid red, you could always tightline with black eyeliner to give that alternate color effect. There are also regular sized cosplay circle lenses that have red and black on them too so there is that possibility to consider, as Digit stated.
Originally Posted by Ion
Regular sclera lenses are 22mm while the minis are 17mm. That is still going to fill most of your eye with a color and give a very big visual impact. The advantage of minis is that obviously with smaller lenses, you can wear them longer and insert/remove them easier than full-size sclera lenses. A quick google search of mini-sclera lenses will give you a good idea of colors/designs available. I have seen the mini-sclera lenses priced at around $30/pair and up.
Annnd, as always, there will be Rize cosplayers who either did not want to/ cannot wear contact lenses of any sort so do not feel like you are obligated to wear them for this cosplay if you are not comfortable inserting, wearing, and removing larger-than-normal lenses. Googling for photos of other cosplayers and what they did can give you some quick inspiration and ideas for alternatives.