If you post the last seven digits of the VIN I can give you the BMW part number. You might as well check the price of the dealer.
I tried looking in TIS by just entering your make and year, and it acts like your car doesn't have an oil cooler. It's not mentioned in the Bentley manual or at bavauto.com, either. If you've seen your oil cooler with your own two eyes than ignore me, but I think you only found performance oil coolers because they are an aftermarket add-on only. I just went and looked on my 92 325is and I don't apear to have one, but mine is pre-VANOS.
Bimmerzone.com has it for $178.92, but it says it's an AT oil cooler. It doesn't look like the one on my E30. I'm assuming AT means automatic transmission, so this might or might not be what you're looking for.
1988 325iX Alpine White
1992 325is Dark Metallic Blue (?)
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