unless you are particularly attached to it and presuming you have tried ordainairy jigsaw blades to no avial (you have tried ordainairy blades havent you?)
I suggest that due to the price of jigsaws that you throw it away and buy a new one.
I am being serious, it is a shame but sometimes you will spend more money than what the product (saw in your case) is worth trying to get something you can not get because it is obsolete, take a cordless drill for example, my first one cost £150 it was only 9 volt, with hammer. You can now buy one for less than £20 (o.k their rubbish), but a good one can be had for less than £50 and they are 18 volt (iknow i have bought two, "lost the first one" found it lost it again latest one was £49.99 18volt with hammer, variable speed etc etc, doesn't make the tea, but it will stir it
I rest my case.