If you google the term 'grab button' you will find lots of resources to help you design your own button. Most use PicMonkey, though I find Pixlr easier to use. I found designing the button took me a while, and mine certainly isn't great, but the tough part was getting the code to work! Where a box is meant to display the code for others to copy and paste, mine kept coming up blank. No matter how many tutorials I tried, or how many times I checked the code it just wouldn't work.
Read more to read how I fixed it!