Not sure of the older shroud length, but Salty Dog has them:
https://www.ebay.com/itm/HOBIE-CAT-16-SHROUD-WIRES-BLACK-2-1971-1994-NEW-2-259412-/131728669101?vxp=mtr&hash=item1eaba3f9adThere's a lot more to running more mast rake than just the shroud length. If you have the older 5:1 main blocks and/or your mainsail is over stretched vertically, your main blocks will go block to block before the main is fully sheeted. More rake also loads up the rudders more, so other upgrades/adjustments may be needed there. With the info provided, it sounds like the older length shrouds are the way to go.