It is NOT possible to rent canyoning equipment in the Nelson area.
Or anywhere else in New Zealand for that matter.
You must plan to bring all your own canyoning equipment with you and be self sufficient.
There will likely be people who will be willing to allow the use of their rope during a group trip, but don’t rely on it. Bring your own stuff!
The only exception is for people going on paid, guided trips with Abel Tasman Canyons. They supply all the equipment needed on paid trips. Contact them directly to organise your trip.
There is a discussion on canyoning gear for NZ conditions on the KiwiCanyons.org website.