There are two companies that can be very helpful here: Vista Print https://www.vistaprint.co.uk and CafePress http://www.cafepress.co.uk/
Vista Print often advertise on television and offer a special code for a discount. Once you've purchased something, they often offer you a time-limited discount on your next purchase. Take care, though, they're very good at up-selling and cross-selling. You need a thick skin.
Vista Print is slightly cheaper but you're expected to purchase one of your designs straightaway. However, you can have them dispatched to a third party. So this might be useful for gifts at an online launch. CafePress has the advantage that you can design items and leave them in the "store". You can even get your fans to buy them. Again you can have items sent to a third party.
Items you might consider
Postcards, bookmarks and business cards
Bookmarks are rather obvious though here's a thought. At your event you want people to buy your book so why would you advertise it on a bookmark you give away free? Might it not be better here to have something about your backlist? Or about any services you offer? On the other hand, you can often leave a stack at your local library or if your book is appropriate at your local primary or secondary school. Take bookmarks that advertise other books to your event.
Book front-covers fit both postcards and business cards beautifully. Your postcard should have the front cover on one side. On the reverse you should have the blurb, information about where to purchase the book and a short bio. You may leave some blank space so that you can sign them for people. I always take a heap of postcards on my school visits to give out to youngsters who can't afford to buy the book. They often want an autograph but if they just collect it on a scrap of paper it will probably get lost before they've even got home. They'll be proud of the postcard and you're supplying them and their parents with information about the book which they might buy in the future. You might also get permission to leave postcards at local businesses. You can use them personally as a place to write notes for other people you meet. Keep a few with you all the time.
Business cards should have the front-cover of your book and on the other side you should have your contact details – if only an email address – and information about where to get the book. These can be slipped into any snail mail you send, inside other titles you send out and used as your regular business card.
These are always fun and I tend to make myself one every time I have a book out. Both Vista Print and CafePress allow you to produce "carousel" mugs. You can have multiple book covers running round the outside of the mug. My latest mug always becomes my default mug.
This probably won't do a lot for your sales though arguably if you collect a few you could consider using them at an event especially if you hold it in your own home. It's good, though, for massaging your own ego and building up your self-esteem. It might also help you to say "I am a writer" to the rest of your family.
T-shirts and other wearables
Yes, you wear your advertising. I've had ones made with a front cover on the back or the front and others with lists of all my titles, colour-coded as to whether the book is fiction, non-fiction or educational. I wear the T-shirts to the beach and the gym or as casual summer wear. They make a subtle impact. They remind everyone that you are a writer. And they're T-shirts, after all, if you need them.
Pens and notepads
These do make excellent gifts, particularly at events. The pens and the notepads are useful anyway. Every time your fans use them they are reminded of your work and that you are a writer.
You could give these to loyal fans or anyone who buys lots of your books at an event. It will serve again as a constant reminder of your work and that you are a writer.
It's possible to make a calendar with a different front-cover for every month. I once made one like this as gift to each of the people who work with Bridge House. It was well received.
Would this work for friends? Maybe ones who are interested in art or in your writing?
Again, this might just be something that will help you feel good about your writing.