There are several on eBay, but the asking price is around $800 US. Suppliers, when they have them, sell gimbals for the P2+ for around $700.
I would not buy a gimbal second-hand.
What is reprehensible, in my book, is people selling Vision Plus's on eBay with bad gimbals, and implying this is an easy fix, or "I don't know".
If you've crashed it and damaged the gimbal, it will need replacement under most circumstances. I see birds for sale with statements like 'just a little something wrong... minor damage... goes flaky sometimes... I don't know' etc. Yep, I was pissed when I broke mine 2 weeks out of the box too, but it was my fault and my loss. Trying to stick it to a newbie is just wrong IMHO. I'd like to sell my busted one, but I'll either have sell the bird without the gimbal, replace the gimbal myself and sell the old one for parts, or just keep it. which may not be a bad idea, because DJI may very well come out with a better gimbal/camera as an upgrade or the price of the replacement gimbal may drop over the next 6 months. By which time, I probably will have broken this one.