Custom antibody production services are basically services that will develop an antibody for you! They can even start at the peptide / protein purification stage and hand you a purified monoclonal or polyclonal antibody!
You can have custom monoclonal antibody or polyclonal antibody to be produced. There are many companies which provide services for antibody development.
If you checked the interet and the protein you are studying does not have an antibody, the next best thing is to get a good company to make it for you. Monoclonal antibodies are good for western blot, protein phosphorylation studies, immunohistochemistry, ELISA, and many other molecular biology methods. You probably need a monoclonal antibody to be made. You need purified protein to inject into a mouse to generate your monoclonals. If you don't have pure or recombinant protein, you could try peptide antibody production which uses small pieces of your protein synthesized as a peptide as the antigen when injected into the mouse. The only problem with peptide antibody production is if you are studying protein structure, motifs or structure you may be out of luck. See custom monoclonal antibody production for more information.
Often you look for your antibody of interest and it is not in any antibody catalogues. If you are looking to make an antibody for either immunoprecipitation, total protein western blot analysis or similar methods then you need custom polyclonals to be developed. See custom polyclonal antibody production
If you do not have a purified protein and need an antibody, it may be a good idea to make a peptide for the protein that you are interested in and use this to generate an antibody from either mouse (monoclonal) or rabbit (polyclonal). Many companies have services that combine both peptide synthesis and antibody development, and include rabbit or mouse injections and bleeds. The benefits are quicker turnaround time usually as one company is doing your work and you do not have to ship your peptide back out to another company to make your antibody later.
The problem is that with peptide antibody production you have an antibody against a small sequence of your protein, so you may be out of luck if you are studying anything other than protein expression.
Monoclonal Antibody Production
Phage Display Antibody Production