I had some difficulty getting a filter cartridge locally ( Halfords compatability chart no longer goes back far enough to include 2CV ) and my local motor parts store was'nt much better.
So I did some Googling and found a list of compatable cartridges, so here it is
(same as fitted to Citroen 2CV & Peugeot 205 & 309) UFI part number (23.105.00) corresponds with;
AC Delco FX0011 (was X4A)
Champion 101
Cooper Z64
Fiaam FT4654 or FT 4847
Fram PH2839, PH2864A
Halfords HOF216
Knecht OC 5 (equivalent to Ducati #065149960 and #090549960)
Mann & H W712/9, W712/11
Motorcraft EFL 47
NAPA: 1352 (1352NAPA and 551352 on the box)
Powertrain FL125
Purflux LS131
Purolator FC 103 or OC 5
Tecafilter Ref OC5
Technocar R12, R72, R434
TJ FB2094
Unipart GFE 201
Hope this is of use
All the best - Bill