get a set of aftermarket turn signals instead. the only way you are going to get an integrated turn signal kit is if you mod the tail to a later model or make the kit yourself. i use a set of Shock Racing LED turn signals. small and bright.

you will not find much in the way of aftermarket accessories strictly for the 87-90 cbr's.if you are creative, you could try to use aftermarket items from other bike years/models to suit your needs.

a good chunk of this forum is DIY as far as aftermarket stuff goes.