Side dinette bunk beds

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We have just bought a lovely Avondale Landranger 5500 with a side dinette which turns into single bunks. The top bunk is missing some parts, it only has the fold up base that sits against the wall and some sort of barrier boards to stop kiddies falling out.
We were aware of this before we got the van. I'm not sure what 'bits' we need to make it a working bunk. It seems a bit cheeky to get a dealer to show me on his forecourt vans, and I don't know anyone with a similar model. Also, is it easy to get spare bits
like this? I'd appreciate any help, thanks.