I'd suggest you do a google search for "USB wireless modem access" or something similar to see if there are products in the US that will do the trick. There are some USB adapters that allow you to hook up PCMCIA cards.
In Australia, I use a USB wireless modem to access Telstra broadband services, and it works fine...not as fast as the PCMCIA modem I use in the US, but still workable.
I wouldn't recommend wifi on win98SE...there are too many issues involved with USB compatibility and you'd have to use whatever wifi software comes with the device, which I've found to be universally buggy on anything aside from XP...
But, since that wasn't the answer you were looking for D-Link makes a nice little USB wifi dongle the DWL-G122 I'm fairly fond of. Works well on older IBM laptops. I keep one in my bag at all times for wifi network testing at my client's sites.