I suggest to use antibody from cell signalling. They have two kinds of CaMKIIalpha antibodies one which identifies only CaMKIIalpha isoform and the other which identifies the other isoforms of CaMKII the beta and gamma isoform in addition to CaMKIIalpha. I tested both of them on proteins isolated from skeletal tissues and they both work good. Good luck with your blotting.
We have a CaMKII alpha monoclonal antibody (Catalog # SMC-124D) that has been tested for use in WB and rat tissues. I've attached the link to the product page. We offer an antibody trial program where we can send you a free 12ug vial of the antibody, you just have to pay for shipping to your destination (~$45). Let me know if you would like to try it out, and I can have it shipped to you for use early next week.
You can check a free antibody database available at labome.com. With regard to antibodies to CaMK-II alpha, you can follow this link: https://www.labome.com/review/gene/human/CAMK2A-antibody.html. In addition to antibodies from Cell Signaling, Santa Cruz Biotechnology has CAMK2A rabbit polyclonal antibody (Santa Cruz, sc-9035) was used in western blot on rat samples at 1:500 (ref: Lv et al., Mol Med Repr 2015) and goat polyclonal antibody Santa Cruz, L-15, sc-5391) used in western blot on rat samples (ref: Zhang et al, Hyppocampus 2015). In addition, Invitrogen has CAMK2A antibody (Invitrogen, 13-7300) used in western blot on rat hippocampus samples (ref: Domínguez-Alonso et al., Int J Mol Sci. 2015).Also, Abcam has CAMK2A antibody (Abcam, ab32678) used in western blot on rat samples at 1:1000 (ref: Sadredini et al., PLoS One 2016).