Okay this is a variant on the rat poison but here is what I'd do. The 'ol PEANUTBUTTER CUT MY FOOT trick....
The typical rat poison you get works by blood thinning, so you can enhance its effect by bleeding it out.
1) Get an old wine glass that you don't like. Add it to a cloth sack and smash it with a hammer into little pieces. Crush it enough to get nice tiny fine little jagged pieces not big pieces. I suggest a wine glass, because they tend to be thin. I'm sure if you look in your collection you will fine one with a chip somewhere that can be sacrificed.
2) Now take a good sized piece of cardboard. Coat a section of the cardboard about 1 sq ft or larger with elmer's glue (or any white wood glue). Sprinkle the glass shards onto the glued surface and let that baby set overnight.
3) Take a nice dolop (tablespoon) of peanut butter (hey its just a rat - use the no-name stuff) and make a pile of the stuff in the middle of the glass shards. Smooth a hole in the centre of the peanut butter. Tumble in a bunch of your rate poison pellets onto the peanut butter hill. Mix it up good, getting that yummy peanut butter all over the pellets.
So here is the deal - stealth rat thinks he is all clever like but cuts his foot while sauntering over to rat poison. Gobbles down his peanut butter goodness. Might even cut his tongue while gobbling up. The he bleeds out all the while thinking - man that peanut butter was good - I really screwed Ilbruche again...