There was square front LOMO anamorphic lens 35BAS12-4. Like any other LOMO anamorphic, it consists of the front anamorphic part and rear spherical part.
For sale is such rear spherical part OKS2-30-1 made at CKBK in 1966. You may use it as replacement block if your lens is damaged.
Also, you can use this thing as standalone 30mm lens if you find a way to mount and focus it. Or you may buy it for your exposition since this type of lenses is very rare.
The block is small - 37mm rear thread, 51mm length.
Excellent optical and mechanical condition.