Bought necks from Kmise UK and Jinwan.
The Kmise necks were something daft like £24, 3 maybe 4 year down the line still well impressed by them.
I also found the Kmise UK folks to be up front and honest. I placed an order just as China went into lockdown then had a message from them saying they expected some delays and it'd be best to cancel and find the parts elsewhere. Being an derrière I told them it was OK and I'd wait , took them 6 weeks of messages before I followed their advice 😆 Another time they miss some eBay time limit for shipping, that message was " We've run late with dispatch so refunded your money but goods are in transit. Could you contact us when the neck arrives so we can issue an invoice."
Couple of days later the neck turned up, I asked for the bill and happily paid the balance.
Have 4 necks from Jinwan, not through eBay but their Ali-Ex store front; worked out cheaper 🙂
Proper chunky 51 P-bass necks, been very happy with those as well.
3rd eBay seller to look at is 'twincam'. Willie gets the same necks/bodies as the 'Musicily' brand sells, ships from England so you won't be waiting long.