Lipcote is a great product to keep in stock to make your lipstick last all day. It comes in a handy nail polish style component and brush, so you can swipe the product easily over whatever lipstick you've applied underneath. There's a strong sting as the product dries down but it only lasts maybe 20 seconds or so.
It's super cheap and can be bought from Boots and Body Care in the UK for less than £5. I always stock up whenever I'm back!