I got a CMP 1903 that came with an A3 stock....not correct in my eyes but I’m anal like that. I went to the CMP forums online and navigated to the classifieds (can’t remember if I visited the 03/03A3 forum first or not). Found bunches and bunches of parts for both variants and stocks were plentiful. Got me a period correct stock with zero hassle.

You only live once, but...if you do it right, once is enough.