here is the ali-express selection of replacement GPS units.
http://www.aliexpress.com/wholesale?spm=2114.01010208.8.37.GJdLuL&initiative_id=QRW_20160220084911&SearchText=x380+gps+module&productId=32456187385
They do have other cheaper modules but I'm not sure if they are compatible.
http://www.aliexpress.com/wholesale?spm=2114.01010208.8.37.GJdLuL&initiative_id=QRW_20160220084911&SearchText=x380+gps+module&productId=32456187385
They do have other cheaper modules but I'm not sure if they are compatible.