The jackshaft is a short shaft that couples the RH driveshaft to the gearbox. Lotus incorporated the jackshaft to allow the driveshafts to be the same length, thereby minimising torque steer.
The Lotus part number is A100F6033F (item #5 below):
The bearing can wear out but it is a bog standard 6206-2RS plain single row, ball bearing type with rubber seals (30mm x 62mm x 16mm) and available from any good bearing supplier / manufacturer (SKF etc.) which may be picked up for ~£5. There are also two nitrile rubber seals, sizes 43mm x 56mm x 9mm and 38mm x 62mm x 8mm which are available for a few GBP.