Trunk release buttons where an OPTION only. Most cars did not have them, unless you have a top of the line model or you ordered special packages with the car.
If it has a trunk opener, it is in the glove box. Open the glove box and if you see a button on the inside edge you are good.
Other options. Go in through the back seat.
Lift bottom cushion out and then unbolt the back cushion which is attached on the bottom and lift or bang it UP and out.
You may have to remove the sound deadner/trunk seperator and then squeeze through the braces.
You can then use pliers to grab and turn the lock rod that goes from the back of the trunk lock to the catch mechnism in the trunk.
good luck.
There are really no other options then to go in through the back seat. If you try to take the trunk lock out from outside of the car you will most certainly destroy your trunk to do it.
I suppose you could call a lock smith and see what options they give you.
Also, If you know what dealer the car originated from, you MIGHT be able to get the key codes from them and cut new keys, although given the age and such it may yeild nothing.