So if we're looking to reduce the number of devices to just one, we want a USB-Eth adapter that is externally powered. There aren't that many of them out there. There are a few brands carrying this one but the reviews complain about the quality of the plastic. Also, there is this one. Compatibility should be ok, because it is based on the Asix AX88760 chip, which Asix's web site says uses the same driver as the AX88772 (which the N900 with power kernel recognizes, as shown by my usage of the Trendnet and Plugable adapters). However, Syba says it will 1) only operate when the external power is on and 2) it will not charge the host (N900). Ideally we'd have 1) and 2) but I guess we can live without.

An alternative would be to get a powered USB hub and use it with the existing USBEth adapter. This way we'd get 1) and 2) in exchange for operating two devices.