Your best bet is to do a VPN. You can get all kinds of cheap Linux boxes with multiple Ethernet interfaces (for example, check out the Portwell PNA-3303). Then, you can ignore the WEP/LEAP stuff that never actually worked and use generic, cheap base stations and wireless cards. Likewise, many new laptops are coming with 802.11b built-in. If your solution requires a non-standard card, then you can't take advantage of these new laptops.

If you want your wireless network to be effectively "inside" your network, with sensitive traffic going wireless, VPNs are the only safe option available to you. (Although, you could do it on-the-cheap with SSH tunnels and HTTP proxy servers.)