You can easily get ARM MCUs with parallel bus interfaces, stick a CPLD on and you can make ISA out of that. The trickiest part is likely ISA DMA emulation. e.

You can easily get ARM MCUs with parallel bus interfaces, stick a CPLD on and you can make ISA out of that. The trickiest part is likely ISA DMA emulation. e.g. STM32H750 (< $10, Cortex-M7, 480 MHz, 1MB RAM) should easily give you room for emulating a 486.