There are several wireless routers that have a modem (console) port. All that I'm familiar with have a 9-pin, PC-style "COM" port, to which you can attach a PC modem.
For example, the SMC7004AWBR has both two external antennas (very good for range and coverage) and a COM port. This is an 802.11b product. D-Link's DI-824VUP also has a COM port, one external antenna, and it's 802.11g. Their DI-713P is an 802.11b device with a COM port and a parallel print server as well. USRobotics has the model USR8022, which again has what you need, and is a "B" device. Asante' also has products with the COM port required for the "fall back" modem connection.
All of the devices I mentioned include a 4-port ethernet cable/DSL router, as well as a wireless access point and COM port. They range around $110-130 list.