Any pics? Just wondering if they are the same as on the very early cars? SEV type where the arm clamps onto the spindle.
EDIT. Just checked the parts catalogue, they look slightly different to the early (meaning 1960's type) cars. Do the spindles come apart after soaking in WD40? Sometimes they canbe pulled apart and the shaft greased and inserted back into the threaded surround.
Have you tried a Renault dealer? I have a car of that age awaiting restoration but it also has seized spindles so can't help with spares. I should imagine this is a common problem.
My approach will be to remove the spindles from the car and leave them in a bath of diesel for a week, then try to unseize them in a vice. If that doesn't work I'd be very interested to find out if they are available from Renault.
We tried our local renault garage - we are in France - and they want 200 euros - £150 which is how much we paid for cynthia in the first place! Hubby says the spindle had seized and that because the inner part is aluminium and the outer part is steel it's impossible to free it without breaking it. The seized up spindle seems to have burnt out the motor so we are looking at a new set but not at renault prices! Cynthia is a 1974 R1126 and the wiper motor is a S.E.V. MARCHAL.
That is tres cher. Best bet is to find a car in a scrapyard and remove the bits. I believe any version of wiper motor assembly will fit any Renault 4 so long as you use the wipers too - they changed somewhere around 1973.