Not sure if this is of interest to you, but ffordes (https://secure.ffordes.com/index.htm
) have a single-coated Voigtlander 40/1.4 Nokton in their used section for £199. It's not an exact match for an R2A, but it is a lovely fast and compact lens (FWIW I have one for my R3A, and ain't nobody taking it away from me). I've also seen Voigtlander 35/1.7 LTM on eBay recently for £160-£180; that plus a second-hand adapter would fall well within your budget.
Will a J-12 mount on an R2A? I seem to recall that the rear element of mine fouled the front shutter of my R3A.