Per the manual, what part are you talking about? The blocker lever or the plunger under the rear sight?
The 85 uses a different sear/blocker system than the 89s. I'm pretty sure the firing pin is different too which would yield a different plunger.
You will probably have to buy a parts kit off gunbroker or ebay to get the parts you need.
Post pictures and we will help more.
An additional problem for you is the 89 was made for a lot of years and they changed them from time to time. Meaning your guns may be old and take different parts than a newer gun. Pictures would really help.
Welcome to the forum!