How to find a pine/spruce (or similar) tree?

Check with your local nursery for suggestions

I planted a miniature mugo pine, but mine died. So they make them.

Mugos won't grow in your area these are a mountain pine need cold winters higher elavation only to zone 7 Any cedars,pines trees etc. will grow a certain size even the Mugos just need to prune to keep size you want them to be in the area you put them in.(example Bonsai full size trees in miniature) try a Dwarf Japanese Garden Juniper or Blue Angel White pine or Weeping Blue Atlas Cedar or even Deodar Cedar these can handle temps and conditions will need to train/prune to size you need even tho' they are slow growing check online for sales if you cannot find inyour area due to your zoning

There’s lots of Dwarf varieties of all conifers.