Sid...I think I could write a thesis on White Walls!!!
There is a company/item called 'porta-walls'. They are widely available and pretty inexpensive.
You can purchase them at Lucas Antique Tires:
http://www.lucasclassictires.com/
They have the best prices around...about $45 for a set of 4.
Now, there have been quite a few folks(on the volkswagon boards) which have complained about using the porta-walls, Some have had a hard time having them mount properly. Others had issue with them 'flopping' around at highways speeds. Yet others have complained that if you ever even slightly scrap a curb, the porta-walls tear. Lucas tire recommends using tubes if you run porta-walls with radial tires.
But on the positive side...you can't beat the price. You can by a set of 155/80/r13 tires at your local tire shop for $100, then add the porta walls and have a grand total (including mount/balance) for about $200.
I highly recommend speaking with Lucas Tire...They are good folks and were very willing to discuss & answer questions.