Those are a really easy thing to do yourself, they're just the joiners that're used on pool and snooker cues; the trouble with them is that they're not very strong at all, it doesn't need much sideways pressure to knacker them.
When I made sectional staffs and walking sticks i used the big brass ferrules from a set of Victorian chimney brushes, very strong and they look great but take a little longer to fit. Many folk used to ask for this as a mod. to their favourite stick so as to be able to get it onto planes and public transport.
You can try
http://www.thestickman.co.uk/, this guy carries a range of stuff for everything you'd need for to dress a fine stick and is not too expensive, either. And of course now for the next couple of months is precisely the right time to go cut a really nice stick for yourself!