There are all kinds and sizes of "slam latches". You just need to find one that fits the configuration you have. What year/make/model of RV are we talking about, and what sort of latch does it now have? A picture might help.
Here is one source for slam latches:
http://www.reidsupply.com/products/fasteners-hardware/hardware/latches/slam-push-to-close-latches/