I found a used CK-40 for $299. and like I said you don't have to use it in stereo mode but is there if you choose to have it.
On the site that I linked for you there are other microphones that aren't stereo with multi-patterns.
Avantone is a great microphone company.
An other LDC that you may choose to check out is the Se Electronic microphone line. A fast google search will bring you to their site or to the numerous articles of praise.