I have a pair of Fulcrum Racing Sport wheels that came with my Bianchi. I always like to have a spare rim on hand in case I destroy a wheel and have to do a laceover. The front is an 18h radial job and front wheels are seldom a problem for me anyway. The rear is a 24h and as I look at Fulcrum's catalog it looks like the Racing Sport rim is a 24mm deep rim with a 20.5 width. The closest rim I can find that may work is a Sun Ringle Venus which has a 590 ERD, a 25.1mm depth and 20.4mm width. I do not know the ERD of the rim that Fulcrum uses with their Racing Sport wheelset.

The Venus looks like it would work but wonder if there are any other with close dimensions. I have had good luck with their Assault rims.