I would lean towards the buying an ashtray from Walmart; when we bought the wife's car last year, I asked about purchasing the optional "smokers package", which consists of a removable ashtray that fits in the cup-holder, and a pop-out lighter. The cost from the dealership? $99.99...
But yeah, having seen my province on fire for the past few years, I have to echo Tommy's sentiments; I picked up a couple of "extinguishing ashtrays" at the local Dollar Store, no reason other smokers can't too - especially those of us still smoking cigarettes; if we can justify the cost per pack, we should be able to justify the $2 for an ashtray.