I could do with one of these myself. The manual gear lever has one hell of a throw to shift each gear, honestly I own cars from the 70's and early 80's with a far more close and precise shifter.
The best way to source something that will be useable with the Forenza gear linkage would be to cross reference it with other cars with a similar engine and box. Chances are an older version of a Vauxhall (Opel/Holden/GM) Astra will have a similar gear change and perhaps there are aftermarket shortshift kits for the SRi. The only problem maybe that the gear throw is quite long for a reason in that it's a bit notchy, especially from a quick up change from 2nd to 3rd, it's really easy to miss.