What is the i486SX chip you are currently using?
Is it a i486SX-25?

You never said what the clock speed was of your processor.

The reason I am asking is that I have a i486DX2-50 sitting in front of me.
It has 168 pins
It seems as though it would be compatible with a i486SX-25.
It runs with a system bus speed of 25Mhz


If the chip I have is compatible with your motherboard, then it is yours.

Please let me know if an i486DX2-50 will work with your mobo, and I will send it to you at no charge.

Please note that the chip is also untested, and I do not know if it will work.

You get what you pay for, I guess.