Update - well the bargain eBay belt (£162) never arrived, so I got a full refund. "Courier lost it" - well the tracking number never worked, so I'm a bit suspicious despite the refund.
Anyway - back to the web, found the same Conti HB135-118 belt for £127 posted from "Spareto" online.
https://spareto.co.uk/products/contitech-timing-belt/hb135-118Suspected it was a Euro supplier, although a .co.uk domain and all prices in Pounds.
Ordered it on 12th, arrived today (19th) via DHL Economy Delivery, from Estonia. Under £135 means no VAT or duty, so it came straight to me.
It is in a Continental box with a QR code to their website for product details which works, and is marked for HD Softail Deluxe 08/06-12/11 and Softail Convertible 01/09-12/11.
Install before 4/2028.

The belt itself is marked as "Made in USA" with a date of 15042023, so I guess made last year, and a part number 523935937.

Looks all good, and a major saving. Now letting it warm up before straightening it out - it's not kinked but has been in the Conti box a while (one assumes they choose the box and package it to avoid damage).
Once fitted I will update this thread (hopefully NOT from a roadside.....)