You need a PCMCIA wireless or ethernet card (not sure about a modem card), also known as PC Card Type II or Type III according to the specs of your Toshiba. I don't know where you live, but if in the US, check Newegg. I found a D-Link wireless card at Newegg for my old laptop for $16. If you are using Windows 95, I don't know about the drivers you will need and I don't know if W98 has any either. I'm running Linux so no problem for me. Your slots are 16bit.
Update: You can also try a PCMCIA modem card.