If it is not possible to convert your machine, how about running a copy of the R 1 or 2 onto a videotape, then record the tape copy onto your R4 machine.
Quality will suffer here, but it could be "cleaned up" and would then give you an R4 copy.
The cheaper option these days may well be just to buy a multi or R1 / 2 player and use it to watch that disc.
I must be honest DVD is not really my thing, but see no reason that this will not work. Only that you may have to use an old VCR to miss the Blocking signals on your disc.
Hope this is of some help,