I don't think there's a spare 13mm, but I'll check in a bit.
245/40-19 is theoretically the correct size but IIRC that size is not very common, and would probably look a bit daft on 9.5s. 255/40 is only 1.5% rolling radius larger so not a big deal, and as Ricky says will give a subtle stretch depending on what tyre brand you go for. There is a significant difference in the carcass width between brands for the same specification so for example Goodyear, Kumho and Pirelli are quite wide fitting so suit a wider wheel whereas Chinesium like Nankang and Accelera are quite narrow and so look a lot more stretched. I'll grab some pics later
