The Kiev 4 case is slightly wider than the Contax IIa/IIIa case but the tripod post lines up perfectly (which isn't true with an earlier Kiev II/IIa/III case). OTOH a Kiev 4 case won't fit on a Contax II, for the reverse reasons.
It's everything but a "poor fit". And the Kiev 4 case leather (supple, well tanned) is noticeably better than the original Contax IIa/IIIa one (brittle and crackly). Also the Kiev 4 case interior is made of red leather not that pesky red cloth.
I have both for my Contax IIIa and the Kiev 4 case has a way better feel than the original.
The light extra space on the camera sides allow for fitting the neck strap on the camera body eyelets which is barely possible with the original case that was designed to have the neck strap attached to the case itself.
Besides I keep wondering what and whom the previous threads of the forum were written for, since an advanced research would have got that thread retrieved :
http://www.rangefinderforum.com/forums/showthread.php?t=57589