There does not appear to be a Jobo distributor in Ireland so probably your best bet is either the UK (www.novadarkroom.com) or a Euro-zone country if you prefer to deal in Euros... The red caps are only 4 quid in the UK. Postage will cost more than that, so try a local dealer first - they may be able to order one if they do not stock it.
Should be a normal spare part. You'll likely get the whole lid without the insert. Make sure you get the rubber cap to. Then remove the insert from the lid you have and put it into the new lid. If you want to use both lids without changing inserts then order one to. Either the film or paper cup.
I don't think there is one available for lids with fitted cogs. It would be necessary to buy a new lid ... or... If one is really cheap ... ahem!!!
I .... uh .. this cheap person I know ... visited the local hardware store and bought a run-of-the-mill Rubber Stopper (available in a wide variety of sizes). Works perfectly.
Fintan do you need a lid or a red rubber cap? If all you want is the rubber cap then go to anyplace that sells winemaking supplies. They should have a rubber stopper big enough.