Originally Posted by
espritduo
To be specific, the Geckorex/Basilisk only appears in the grassy areas of the Jidoor/Zozo continent and the Narshe continent in the WoR. Anywhere on those two continents will work, but it has to be on the grassy areas. Also, the Basilisk has a 6/16 (37.5%) chance of being encountered on the Jidoor/Zozo continent (it has two identical encounter formations possible, a 5/16 one and a 1/16 one), and a 5/16 (31.25%) chance of appearing on the Narshe continent (it only has one possible encounter formation there, the 5/16 one).
EDIT: I also updated the wiki, so now the precise location is listed there too.
EDIT EDIT: And I guess I can mention that when it comes to Morph, all items have an equal chance of being morphed. There are four slots for morph items, and each slot has a 25% chance of being picked. Sometimes the same item is in multiple morph slots, so that item will naturally be picked more often, but the base, and therefor minimum chance of any particular item being morphed (assuming the morph chance doesn't miss altogether) will always be 25%. In the case of Cactrot/Cactuar, the base hit rate of Morph is only 12.5%, and the Tortoise Shield occupies one slot (thus, 25% chance, same as any of the other potential morphables), so you've only got a 3.125% chance of any given Morph attempt getting you what you want.