Ah my apologies... When you said it was a 2 litre CR engine I assumed it was the 170 engine. Completely my fault... I had the sump off my CR170 a few months ago to replace the rear oil seal and knew it was a chain I had seen on the oil pump.
To be honest, given how long it has lasted I would just fit a new belt. It's very unlikely it will be a
problem for you again. You would have to swap out the crankshaft and oil pump if you wanted to move to the chain setup. That's more hassle than would be worth it IMO.