My 2009 1.5L Impreza needs a new sensor, OEM number 22690AA940 but I can't find this part in the U.S. I would like to replace it with a good quality sensor. Any suggestions on getting this fixed without looking for this part overseas? Maybe some other oxygen sensor will do?

I see the 2.5L trim uses two 22641AA360, could this sensor work, after replacing the connection socket with the old one?

Its the grey one.

In theory as long as you have one with a matching thread any decent (eg bosch) wideband sensor would work. Just check the signal voltage once you have replaced it other wise you will generate an error - some may require a calibration.

Although a UK site - this is quite cheap

http://www.ebay.co.uk/itm/FOR-SUBARU-IMPREZA-1-5-2009-4-WIRE-FRONT-LAMBDA-OXYGEN-SENSOR-DIRECT-FIT-/121867934201?hash=item1c5fe519f9:g:dAwAAOSwCypWm7Wx