HPA has a good section on antibody validation.

https://www.proteinatlas.org/about/antibody+validation

Regarding your specific question:

There are numerous vendors that sell recombinant proteins or peptides. In general most characterized proteins will have someone selling a recombinant version. Always contact the vendor and determine how they validate that what they are selling is your protein of interest/contains your immunizing sequence. You may want to do additional validation on your end but in those case you may be able to get the vendor to give you significant discount especially if you share your data. Keep an eye on the what the expression host is and if the protein has any added tags. You can go to the genecard for each gene you are interested, they have referral links to numerous vendors in the protein section. If no one sells your protein you can always have a company produce it for you all the big companies(thermo, Novus etc.) and lots of small companies provide this service.

For Peptides many companies will also synthesis peptides for you. Simply match the the immunizing peptide for your antibody or even better reachout to the company selling your antibody and see if they will sell you the immunizing peptide.

Depending on what you are trying to show it is worth looking at is Origene's KO lysates. They have generated cell lysates that have double KOs for 1000s of proteins. If your protein is present in the WT lane and disappears in the KO lane it shows evidence for specificity. See below for one such example with a protein you listed:

https://www.origene.com/catalog/proteins/knockout-lysates/lc810436/s100p-human-knockout-lysate-locus-id-6286

What is the purpose of your 'validation'? Is this the same as ICH Q2 or Q3 or are you just trying to obtain a known concentration of the antibody?

Jasmine,

Remember, 'validation' is a 'specific' term. It applies to pharmaceuticals including antibodies and involves linearity, specificity, accuracy, precision, robustness...