Hi Tony,
AWM in Canberra have a nice restored example of a 25pdr with an Aust welded trail, saddle etc. It is in storage at the Mitchell annex. Access by arrangement. PM me if you want the details. Conservation restored two in 2008-2009: a riveted version and the welded version.
I'm sure there would be examples closer to home, but who knows what condition they will be in. Murgon's gun is riveted (like Tiaro's), but I suspect you already know that.....
Regards
Mike