You can setup the 3CRWER100-75 as a wireless bridge.
What you need to do:
The 3CRWER100-75 has a WDS tab. You need to enable WDR which is in fact bridging.
Note that you need both devices to have the mac adress of each other for bridging, both devices must be on the same channel and both devices need the same SSID.
There should be no extra hardware needed to bridge both devices. I do not have experience in bridging 3com to a Cisco, but I assume it should be possible as it works fine with linksys., which is a division of Cisco.