On where you are.
There is one on
www.milweb.net
Universal Carrier Mk1* Three Inch Mortar Mounting
This is one of the two most complete examples in the world and features 90% of the original stowage and equipment. The vehicle runs and has been exibited, but needs light restoration to make pristine. This vehicle is only available in exchange for a fully restored and equiped conventional carrier, or other British or Canadian war-time AFV.
07786 190077
or,
there are some in Ontario, Canada. In various states of disarray - fixeruppers to show ready.
Good luck.
Stewart