Which train stations near the Oyster boundary have contactless validators on (train) platforms?

This is not a complete list, but the list of stations set to "continuation exit" (unofficial site) is a good starting point, although most stations are not 'boundary' stations and inclusion on the list does not guarantee a convenient validator on every NR platform:

• Barking [Zone 4]
• Chalfont & Latimer [Zone 8]
• Ealing Broadway [Zone 3]
• Elmers End [Zone 4]
• Farringdon [Zone 1]
• Finsbury Park LU [Zone 2]
• Harrow & Wealdstone [Zone 5]
• Harrow-on-the-Hill [Zone 5]
• Highbury & Islington [Zone 2]
• Kensington Olympia [Zone 2]
• Kentish Town [Zone 2]
• Moorgate [Zone 1]
• Old Street [Zone 1]
• Seven Sisters [Zone 3]
• South Ruislip [Zone 5]
• Stratford [Zones 2-3]
• Watford Junction [boundary station in its own special zone]
• West Croydon [Zone 5]
• West Ham [Zones 2–3] (there are Oyster/contactless readers are near the staircase)
• West Ruislip [Zone 6]
• Wimbledon [Zone 3] (see this map (from the same unofficial site), which suggests that, as of July 2016, the platform for Thameslink services does have Oyster/contactless validators, but not the platform for South Western Railway services)
• Woolwich Arsenal DLR [Zone 4]

Another station, not on the above list, about which I happen to know:

• Upminster [Zone 6] (Upminster has standalone validators on platforms 2–3, which is convenient for c2c services heading out of London, since they are usually on platform 2; conversely, most c2c services heading into London use platform 1, which does not have standalone validators, although it does have a side entrance with a gateline).