There is no simple PAL video cable, the console has outputs for YUV (aka YCbCr/YPbPr?) component signals. Some modern TVs can take these directly (my LG 42LF65 did). Otherwise, the PAL modulator mod gives you the composite signal (slightly better quality than from US NTSC consoles), or you could use the SCART/Peritel RGB modulator (mostly sold in France) for the best quality picture.
A schematic for an RGB-enoder was in the November 1988 issue of the ChicagoTImes, I built this twice, good stable picture.
Then there are upgrades based on the 9938 VDP ("80column cards"), or the F18A for VGA output.