I found a supplier at the National Vintage Communications Fair in Birmingham who had a bunch of old Apple ][ boards with 2MHz 6551s on them. So I bought 'em. I think he was glad to get the nasty modern semiconductors off his stall -- just about everything else at the fair was based on valves (vacuum tubes).
And I got a few more 65C51s from eBay. And they're still listed on the Cricklewood Electronics web site:
http://www.cricklewoodelectronics.com
But I suspect that a few weird suggestions from England aren't going to help you much! Sorry!
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