You can ask any of the Etsy MDF sellers to do custom cuts for you. I needed equilateral triangles of a specific size (223mm?), and I got them custom cut by an Etsy vendor who already sold MDF equilateral triangles -- all they had to do was to re-size their existing designs. I used them to make a D20 Globe project.
I worked with a carpenter, for 3+ years, working with him on various design projects, including a 50W Laser Cutter, making different designs, including 54mm scale walls with cut-out window openings, for rectangular buildings for gaming with Army Men figures. I came up with my own system of holding the walls together such that the corners were smooth, no interlocking system showing on the outside.
Bottom line: if they can draw a 2D line drawing of what you want, or scan an image of the cut-out design, they can cut it out of thin plywood, MDF, or other similar materials, but not plastic, resin, nor fiberglass -- these materials typically create lethal toxic gases when burned by a laser cutter. Most Laser Cutter services only work with wood products, for safety reasons.
Contact one or more Etsy sellers who offer MDF rectangles (miniature bases), triangles, or other shapes for crafting purposes. You may want to shop around, based on quoted prices. Cheers!