I have personally seen potjies at the following places:
Organic Food & Cafe
Dubai Garden centre
It seems like they have potjies most of the time. I bought a no.4 pot and a no.3 pot from them. The cost for both was AED 650. They have stores in Dubai Mall, The Greens and Masdar City, Abu Dhabi. See their website for maps. http://www.organicfoodsandcafe.com/
This is where I bought my own No.2 pot. It was mabe 18 months back and a CADAC brand pot. I purchased it at ACE Abu Dhabi. Since then I have not yet seen a pot again. When enquiring about it from staff they would look at me like I'm crazy. I have heard rumours that at times the big ACE at Dubai Festival City in Dubai will stock some potjies. However my last visit there on 1 December 2011 proved unsucessfull.
I love this store. They have anything from fishing gear to CADAC gear. I have seen potjies there years ago and also heard that they have pots on occasion. However on my last visit to them on 1 December 2011 they had none. Their barbecue section is on the 2nd floor.
On my last visit to them on 1 December 2011 they had no. 1 size pots at their barbeque section. The number 1 pot feed 3-4 people if you don't eat too much. They apparently get pots regularly so I would suggest you have a look there.
I hope this is of some help. If anyone knows of other places, please let me know.
An alternative is the Dutch cast iron pots at IKEA. they feel and look like a "platboom potjie" but unfortunately have a stainless steel lid. I have made a pot or 2 in one and it worked out pretty well.