I ripped the front bumper of my 2005 Toyota ANH10, first-registered 01/05/2005 — the first-generation Alphard (2002-2008), white, 2.4L petrol. Any recommendations on where to source a 2nd hand replacement

I would look on eBay. If you search for "Alphard (breaking,braking)" (some people can't spell...) you may find a few people listing parts from their car for sale (often as '99p, this listing is for one wheel nut'). If you find the right car, message them and ask how much for the bumper. Be prepared to collect, as bumpers are awkward to ship. If doing the sale via eBay, the user will typically create a special listing for the parts you requested which you can 'buy it now'.

Some professional breakers list and photograph every part, but this is a way of doing it without having to list thousands of parts.

If you don't find anything there, create a saved search and enable email notifications and you'll get a daily email with search matches.