First, you need to talk to him. You need to find a comfortable way to start the conversation. You could always take the initiative and do something like get some new lingerie or a new toy. You could initiate sex in a different room of the house or in the car.
It's really a matter of thinking, "Okay, what do we normally do? What can I do to show him that I'm interested in something a little different or exciting?"
Buying toys together can be a very sexy experience. You can even do it online if you don't want to go to a sex store. It's important that you do it together so that you get some things that you will both enjoy.