The fan on the retail Intel HSF is a proprietary design, there's no aftermarket fan that will fit on it. It's all built in to that plastic bracket/clamping assembly and doesn't come apart from it.
Your choices are limited to replacing your HSF (at least the top part of it, the fan+bracket assembly) with another Intel version (ebay is probably a good bet for finding one cheap, unless someone around here has one that they didn't use on their install) or going with an aftermarket version.
Oh, and I suspect your CPU is a 1.6
A as Intel never made a "
B" or 533MHz version of that CPU.