You can just try and get hold of a TTE spoiler (the one that came on the SR; got mine for £60 I think), spray it up to match and fit it? It's what I've done with my N/A, and put a Glanza rear bumper on it. Lowering springs for the Starlet are fair cheap, and you could get hold of a spring and strut package, or some second-hand coilovers. If you're looking for front lips and such, look at scrappies for the black plastic lips. The majority of them you can normally cut down to size and fit. Most common seem to be Renault Laguna lips, and a few from Seats, not needing much modification at all.