EGW (and probably others) makes a picatinny rail mount for the 336/1895
http://egw-guns.com/store/index.php?main_page=product_info&cPath=39_128&products_id=254The Weaver base for the 336 also fits the Camp 9 and Camp 45, I suspect these aren't listed by EGW since they are long out of production. I have used one on a Camp 9.
I was a guinea pig for EGW on seeing if an XP-100 base would fit my Remington 600 rifle, as the Weaver base for the 600 is a poor design. It fit, with modifications.
I would contact EGW and make sure they will accept a return if the 336 base doesn't fit your Camp 45.