Nikon Eyepiece Cleaning/Repair

I recently purchased a Nikon zoom eyepiece on AM only to discover that the top element of the moving zoom mechanism is quite dirty, interfering with high power viewing. Apparently, the only way to access the inside for cleaning is by loosening several extremely tiny hex screws (probably .5 mm) on the exterior of the barrel. Unfortunately, my local camera repair shop tells me that this requires a proprietary Nikon tool that hardly anyone has.

Does anyone out there have experience with these or know of someone who could disassemble and clean an eyepiece like this?

Thanks for any advice you can provide.