SRAM compatible 11 speed 12-25 cassette? I'm looking for an 11 speed 12-25 cassette compatible with a SRAM drivetrain, however I don't think SRAM makes one. 

They list specs for their 11 speed cassettes as follows:

11-25: 11,12,13,14,15,16,17,19,21,23,25 
11-26: 11,12,13,14,15,16,17,19,21,23,26 
11-28: 11,12,13,14,15,16,17,19,22,25,28
11-30: 11,12,13,14,15,17,19,21,24,27,30 
11-32: 11,12,13,14,15,17,19,22,25,28,32


Are there any manufacturers that make a 12-25 that is compatible with SRAM? I'd also be interested in a 12-** cassette as long as it has an 18 tooth cog.
You should read Zinn's articles (a, b, c, probably others) on 11 speed drivetrain compatibility. 

The surprising upshot is this: You can swap a Campagnolo 11 speed, Shimano 11 speed and SRAM 11 speed wheel in for each other and they will work (*). You can put SRAM and Shimano cassettes on each other's freehub bodies. 

The Shimano Ultegra CS-6800 comes in a 12-13-14-15-16-17-18-19-21-23-25, so this is a cassette you can buy and use. 

(*) Zinn notes there might be a tiny amount of indexing adjustment necessary. The SRAM/Shimano swap for wheels isn't really surprising, but the Campagnolo one is.