Ive used a cleaved one from CST that's pretty good for western at least. Ive only used it for westerns at 1:1000, but it says its applicable for IP. You might be able to ask for a test sample
Cleaved Caspase-9 (Asp330) (D2D4) Rabbit mAb #7237
No specific recommendation, but if you want to find more possible sources we list many. Just search here http://www.linscottsdirectory.com/search/antibodies for Caspase 9, selecting "Mouse" from the "Reactive Species" filter and "Immunoprecipitation" from the "Applications" filter. Follow "more info" to suppliers' data pages. Hope this helps.