Although I've been to the "museum" lately, I do not recall seeing ashtrays like that in the gift shop. But I do not doubt their existence.
It makes you wonder if the copyright holder of the Silver Slipper approved of the merchandise. If so, which is certainly possible, then I wonder what the going rate(s) might be for usage.
Do you recall other casino logos that are being used?
Perhaps we (the Club) should start a list of fanatsy trays? Maybe even post scans of these things along side fantasy chips!