Some cooking chocolates are made with oils rather than butter (check the label carefully), but the consistency of these can be crumbly and they are not really nice enough to eat on their own!
The Kinnerton brand promotes its 100g Luxury Dark Chocolate bars as milk-free, egg-free, nut-free, and gluten-free. This is a very rich, flavoursome chocolate great for using in cooking, baking, and eating on its own if you like dark chocolate. Kinnerton also make allergen-free lollipops and really yummy chocolate mints. Seasonally, Kinnerton also make Easter Eggs and Christmas sweets. In Australia, Kinnerton say their chocolate is available at major stores like Big W, Kmart, Target, and Priceline, however I have found that not all stores stock them all the time.
Sweet William make 100g White Delight and Original chocolate blocks and various small flavoured bars. They say their blocks are milk-free, nut-free, and gluten-free. They use soy instead of dairy milk, and the Original bar is a great substitute for milk chocolate, with a lighter and creamier flavour than the Kinnerton Luxury Dark block. In Australia, Sweet William say their chocolate is available at major supermarkets Woolworths, Coles, and IGA, either with the health foods or in the confectionery.
Personally, I love dark chocolate so in all my chocolate recipes I use Kinnerton. Please write in the comments if you know of other brands or stockists.