Yes,you can buy it now and put it in a pot - just make sure the pot isn't huge compared to the rootball of the plant, it should be only 2-3 times bigger, potting up into something larger as it grows.

The only caveat is this - although Skimmia is fine in pots, all potted plants outdoors are at risk in a very severe winter. If the temperature stays below 0 degC DAY AND NIGHT for a week or more, the pots will freeze solid and the plant roots will be killed. This circumstance is quite unusual here though - its much more common to have those sort of temperatures for three or four days, or for the temperature to plunge overnight but to rise above freezing during the day.