You need to look at the motherboard if it's that old and see if there are any free PCI slots.
If you have one, any new PCI modem will work, providing drivers are included for Win 95, but avoid Win-Modems. These use part of the processor power to run and your already short on that.
As regards CD-RW, I'm afraid it's suck it and see. The problem you face, is finding software that will run reliably on '95. Although all modern software uses a form of burn proof technology, your processor speed may stretch that to the limit.