[V8] Power Steering Fluid Source?

[Brad Hartman]

The local Audi dealer sells a liter of power steering fluid for $20.00 plus 
tax.

GAG ME.

I have a slow leak at the rack (that will not be fixed) and I go through a 
liter every three months or so.  Any sources of audi power steering fluid 
that are either

1) cheaper by the liter or

2) cheaper by buying a larger container of it (gallon?)

would be greatly appreciated.  (Note that shipping costs could squelch the 
deal if I purchase out of town, but I'd at least like to see if there might 
me some options to consider.)

Thanks,

Brad
1990 V8 Automatic