RAF uniforms arent really my area of expertise, but since no-one has chipped in yet I will. I reckon you could go one of two ways. Either genuine RAF uniform or replica. I dont know the source of replicas as they arent my interest but others on this site should be able to advise.
If you want to go for a relatively inexpensive option with original items you could purchase an original cap, tunic and trousers. You could get away with a modern shirt, tie and shoes of similar appearance. I recommend you look at photos. I like the Australian War Memorial collection database at awm.gov.au go to collections, database, search raf in world war 2. You dont necessarily need irvin jacket or flying kit for your re-enactment.
There are probably exceptions but it was not standard practise for aircrew to wear a pistol and holster. Some I have talked to flew with a pistol. Perhaps in the Pacific theatre that would be more realistic, though then you would be unlikely to be wearing blue tunic and trousers. In this case you could wear tropical shirt with pilot wings, horts or trousers, cap/hat, flying boots and pistol. There are good photos of RAAF pilots of 75/76 Sqns at Milne Bay wearing this sort of kit.