If all you need is an acrylic sandwich then you can also DIY it with acrylic sheet, just cut it to size and drill some holes for the mounting posts. My concern would be the heat from the CPU, you definitely want to leave provision for airflow and and heatsink.
One thing you could do if you’re going with the sandwich arrangement is to use something like my hillbilly heatsink in the cooling thread to move the heat from the CPU to above the sandwich and then strap a finned heatsink onto the top of that, sitting above the sandwich. It’ll look a bit ugly but should give decent passive cooling.