Hi mate, i've searched the internet high and low for them suckers but had no joy. The closest i have come is and old add on the caravansplus website where they use to sell them, so maybe you could give them a call and see if you can find out who made them for them when they were selling them.
Other than that, you could try find some second hand ones but i've had no luck with that either. About the only option is to buy an old cheap similar camper (with decent lifting arms) and strip any good gear off it and throw the rest away.
I'm in the middle of doing a complete refurbishment of my old girl right now and have had a close look at the arms now that they are off the camper. From what i can see, if my main rivet pin was dodgy, i think i would be trying a stainless steel bolt with nyloc nut and see how it goes.......can't see any reason why it wouldn't work.
Anyway, if you do happen to get lucky finding replacement arms, i'd be interested to know who sells them so be sure to keep us posted.
Cheers