I've just had a look through the usual sites and at present I can only find one example for sale, and the price is a bit "steep". Having owned and sold a Pop Air for my previous Eriba, I can confirm they are a good balance on quality, function, size, price. Ideally you should be looking for a post 2019 version 2 model that will accept a front sun canopy and has a zip out side that allows an annexe to be fitted if required. A good clean 2nd hand example should set you back about £450.
Colin