AFAIK Cosworth made rods, pistons, blocks, etc for 'retail' sale as well as significantly different ones for the main Ford competition engines. Sale of these ceased several years ago with stocks sold off in batches to 2 or 3 locations.
So part numbers aren't really much use as they dried up as a retail supply earlier than pistons and CGI blocks.
If, as I asked, you let me know the pin diameter and compression height, I can confirm if any 'off the shelf' aftermarket rods will fit, or if , as with the road FRS rods, its a unique rod which would have to be custom made.
This of course is assuming you've failed in advertising for original Cosworth WRC rods in all the usual places.
Martin