I think it depends a lot on your comfort with communicating sexual desires. If she's out there shopping with you, you might suggest an anal toy. As asked by Herzer above, does she like anal play? In a lot of cases people seem to just jump into something drunkenly. That's generally a bad way to go about it, alcohol or other drugs are not going to help the experience, if it's something you're exploring you don't want to be stumbling, but if you have a drink or two it can help you discuss things. Best to talk and get some input, but if not, you can surreptitiously work a finger towards her back end (very slowly work your way there, don't just jab!). If she responds positively or negatively it can at least help break the ice. My wife seems more comfortable with me using anal toys than asking her to do anything back there, so see what she's comfortable with.