Hi
There are a couple of options for you.
One. Is called the Mutze cap and is similar to the brandrup one you mentioned. I believe it is not much cheaper than the brandrup but it is made and sold from Germany. There are other forum members who have bought them and are very pleased with them.
I don't have a website address saved for this unfortunately.
Two. There is a cover called the Vanorak and is UK made and can be bought from thevwcalifonia website.
It is on sale for £250 inc p&p at the moment, and comes in several colours. It has three windows and can be placed on to the van by one person. It also has its own bag made of the same fabric as the Vanorak. I have this one, and can confirm it to be both waterproof and windproof with a great fit. As an example I was camping in Caernavon last september when there was a heavy storm and it kept everything out and kept the heat inside. This is best used for winter and early spring late autumn times. I bought this as it was cheaper than the Mutze and Brandrup ones and before the next one was introduced at the beginning of the year.
Three. Khyam They also do a version called the Cozi which is £199 plus PP.
http://www.khyam.co.uk/detail.asp?p=121 ... per%20Cozi
I saw this fitted to California at a camping exhibition in Manchester this year, and IMHO is not as good as the Vanorak. I believe it is made in Vietnam (as is my Khyam motor dome tent is use). The fabric of the Cozi is not as good a quality, and the the bag it comes in was very thin and the fittings to the awning side (if you have it fitted) do not work as well as the Vanorak. There are users in their forum who are delighted with it and can recommend it to you.
The last option I know of is called the pucer screen. This is different to the others as it fits between the hinges and the canvas of the pop up roof, leaving a gap at the rear about a foot long. It is secured with a bungee cord. The link below is from an earlier request about roof insulation. I don't know how much they cost. The maker does not appear to have a website or ebay page. If anyone has the details please let me know.
viewtopic.php?f=17&t=15
I hope this helps you decide on your next Callie purchase.