Thought I might try out a Saurus Old Blood with a Wizarding Hat. That being said, it states that user uses a randomly chosen lore. That being said would a D8 be good enough or how would you go about choosing a lore out of eight randomly.
A D8 seems reasonable to me. Another option would be if you have the magic lores cards you could take one from each, shuffle them and then draw the top one. As long as you and your opponent know how you are going to do it it doesn't matter too much.
If you only have a d6 I find that the easiest way of randomising is simply dividing it in 2 (i.e 1-3 gives me one of the first 4 lores and 4-6 gives one of the last four) until you only have 1 lore left. It might consume more time but works just as well if you ont have a d8 or the cards.