I've generally found it difficult to come across clean sparkle dials available separately for sale. This model is somewhat popular and you don't often see clean ones parted out. If somebody can help you confirm whether Omega still has these in stock, your best bet would be sending it to them for a service and dial replacement, or going to an Omega certified watchmaker that has a parts account. Neither would be particularly cheap, but the only other simple option that I see is setting a few ebay alerts and playing the waiting game.