I had this exact situation. I bought a FAG-170 that had a dead pickup, and I had no luck finding anything that could accurately replace it.
It's a custom pickup shape, and has the unusual low-impedance/low-output design of Alembic Series pickups. So as far as I'm aware, the only ways to replace it accurately are:
1) Find an original pickup being sold separately. In ~20 years of monitoring eBay and Reverb for these instruments, I don't think I have ever seen one come up for sale. Maybe this is more likely in Japan, but it seems like it would be very difficult to find. You could ask around in forums if anyone has an FAG-170 and they would be willing to sell you one of the pickups, but these guitars are so rare to begin with, it's probably going to be difficult to find anyone who even owns one, much less is willing to sell one of the original pickups.
2) Buy an Alembic SC-1 Series guitar pickup directly from Alembic. I don't know this for sure, but I wouldn't be surprised if Fernandes copied the Series guitar pickups exactly, and they sound identical to me (I own both), so this would potentially be the best option - with one caveat. I contacted Alembic about this for my FAG-170 guitar, and the good news is that yes, they will sell it (it's not cheap, but not astronomically expensive), but the bad news is that Mica confirmed that the dimensions changed at some point. A new SC-1 won't exactly match the dimensions of a FAG-170 pickup. I'm not sure how they're different, but you may need to do some adjustment of the screw holes, and possibly even some minor routing - or there might be some minor gaps.
3) Create a custom replica pickup.
#2 realistically may be the easiest option.
However, I did #3. This may be more trouble than most people want to go through, but I wanted to fully restore my guitar, and I wanted the dimensions to be perfect. I created the pickup housing, to match the exact dimensions of the original, and Revel Pickups assembled the bobbin and windings to match the exact impedance of the original. If you're interested in the details, I posted about it here (see 1/18/24 post):
https://www.talkbass.com/threads/fernandes-fab-180-pickup-replacement.1606011/page-2#post-28128022It works great, and looks and sounds exactly like the FAG-170's other pickup, which still works.
For the guitar in this listing, though - one minor issue is that it doesn't include the original pickup. (Argh, why would anyone throw it away??) I was able to dig out the magnet from the original dead pickup, and use it in my new one.
To be clear - there's nothing "special" about it, it's literally just a ceramic bar magnet. They're cheap and easy to find. But the only issue is that I couldn't find a new one that had the EXACT same dimensions.
Honestly, though, you can buy ones that are very close, and I doubt it would make a significant difference to the tone, so maybe it's no big deal.
