Glad you enjoyed the translation, barbe_folle!
There are several items you need to bring with you in order to get monkey to appear in the Crab-Crab Cavern.
A crab helmet
The mortar armor
A bee blade
A chestnut curio
If you bring these five items in, the monkey will appear.
The hardest item to get is the mortar armor.
You have to eat mochi at a mochi stand first, but there are only a handful of festivals that have a mochi stand. You have to go back to the festival area a certain amount of time after the festival is over (having eaten the mochi, of course), and enter the now empty festival area. There should be one guy waiting at the center with the armor at that time.
Since the new year festival's over, the next available time to get mochi is during the flower watching festival at the Peacock Shrine. It runs from April 1st to the 12th. Go there, eat the mochi, and then return later, after the festival is finished, to get the mortar armor. (If you take too long, the guy won't be there.)
The bee blade is one of the prizes for hunting medals in Big Tiger Town. You need to find exactly eight medals to get it. If you need help with any of the other items, let me know. If you're thorough, you should have those already.
I've sent in a version five TM Zero revision patch with a small change. It fixes a spelling error that had been left in the credits. I noticed it yesterday, and DDSTranslation fixed it right up!