I order trace minerals from Premiere1. I order several at a time. Mix one bag with 50# of stock salt. I also offer dolomite lime, you can find it in the garden section as garden lime. Be sure to examine the bag, look for dolomite. Pregnant and lactating ewes need the extra calcium. Lambs will eat it too.
I use the Purina Mineral for Sheep. Comes in a 50# bag. Tractor Supply special orders it for me.
Know that sheep and copper dont mix well. Knowing that, a general mineral block may not be good for the sheep.
We mix half and half goat mineral with sheep mineral. Sheep need some copper (which goat mineral has and sheep mineral does not). Somehow over the years, sheep needing a little copper became sheep need NO copper. So we give them what they need. I have no study or anything official but I know a bunch of large sheep growers who do the same thing and the sheep are hardier so take that for what it is worth.