AS you've found Barrabart, there's not really anyone left here as far as manufacturers go.
A few of the trailer places (Tailors, Warpac, etc) will stick an OzTrail top on a custom trailer for you if you poke them enough. But if you wanted to go down that path it'd be cheaper/better to get them to just build the trailer, then fit it out yourself. It's not hard to bolt a top onto a tub, install tanks/kitchen/batteries, and so forth. That's pretty much the path my brother went down - he's handy with the welder, and it let him build the exact camper he wanted for not much money.
As far as proper camper trailer sales though, I think you're limited simply to the resellers and agents around town. You already know about Tolga Traders, Jayco are down your way at Edmonton now, and that's about all I know.
The other option would be to talk to someone like Rockman about the guys who've custom-built his trailer, see if they'd be interested in doing another job. But his doesn't really have much canvas work - if you wanted a full fold-over soft-floor it might end up too expensive by the time you pay for custom everything.
Do you know if the guys at Tolga still have that Trackabout Extenda?
Good luck!
Matto