Does anyone know where I could find Anti-VS antisera or can anyone suggest another way to identify a r'sr donor?

I think it is unavailable at the moment, world wide.

You could try DNA probing at position Leu245Val.

V and VS.pptx

Thanks Malcolm.  What do you think about using the following criteria to make the assumption that a person is r'sr without having Anti-VS.....

The following must be true to assume a unit is most likely r'sr

1. D negative (of course)

2. V negative (we have Anti-V antisera)

3. C weak positive

4. c positive and e positive

Without molecular techniques, I think that is the closest you are going to get!