I don't think there's much future in that computer, even if you could find a new motherboard and managed to install it. While it's hard to find a new computer with a parallel port, it's not impossible. The Atom, for instance, is a small form-factor computer that still has them built in: https://www.alibaba.com/product-deta...802311738.html
You can also look for another old computer, which are often available quite cheaply, or use a new computer and a USB adapter like the UC100 to substitute for the parallel (printer) port.