Lifespan Bio has a rabbit pAb that they say is cross-reactive with mouse and suitable for IP (https://www.lsbio.com/antibodies/anti-purb-antibody-aa262-312-ip-ls-c290310/299851?trid=0)
Our listings for other PURB Abs are here: https://www.linscottsdirectory.com/antibodies?q=PURB, (follow "more info" to suppliers' pages).