I wish I had a perfect solution for you because that would mean I have a perfect solution for myself!
In my area I've found there is lots of competition for used store display cases.
"Baseball" card shops. Consignment stores. Flea markets, etc.
The "curio" cabinets at furniture stores also tend to be high dollar.
No Ikea anywhere near me.
Even building your own can be expensive, especially if you use the tempered glass instead of the window glass replacement. It takes a really special skill to cut glass. It doesn't take long before broken useless glass panes drives the cost up to what you would pay for a curio cabinet.
An imperfect solution for me has been to buy a sheet of plexiglass and cover the front of a bookcase/cabinet. I do finish it off by using strips of wood to hide where the plexiglass is attached to the front of the bookcase. This does keep dust and unwanted hands off your models.