From memory, Alan had these 16" alloy rims manufactured in Asia. As far as I know, no one else currently does this style and size of rim.
Back in the day, this size rim was quite popular, but I think the 17" rims are what people are looking at these days, so I could understand, from a business perspective, if Alan was no longer getting them made.
Sadly, I don't think there is a 5 stud, 17" rim on the market (in Australia) that is DOT approved. ATW used to do their 19.5" steel rims in a 5 stud, but I am not sure if they still offer these.
As far as singles go, the 6 stud, 17" and 19.5" rims seem to be the only ones that are readily obtainable now.
A sign of the times, I guess...