ItsKuffi

I recently got a Kowa Prominar 16-S. As it is you can't put any filters or stepup rings on the front of it. I know it's possible to put something on here, but I'm having a lot of trouble finding the EXACT products that work on here. Of course I know brands like Redstan / Vid Atlantic / Rafcamera but I'd love to hear about specific products from any of them that do the job so I can slap an ND filter on it.