Washing m/c 240 50Hz Connect to USA dryer plug??

Hi Everyone and thanks for the great discussion last October and November that had the title:
Washing machine 240v, 50Hz --- 240v, 60 Hz?
The machine has now landed ;-) and it's time to test your suggestions. The only connection I can make at present is the outlet of an electric dryer. I looked for a suitable plug to connect into that dryer outlet but cannot find one. I visited several big electric outlets, including Home Depot, and they do not stock them. I was told it is Plug 1030R and costs $3.50 by an electrical wholesaler with orders of $100 minimum. I have a 240v extension box, with the correct European outlet for the washer, that takes up to 3.5 kW (washer max is 2.1 kW) and had planned to connect it into that dryer outlet. That would be the easiest route but I would need help with the wiring. I understand that older US dryer circuits, which this one is, have some unusual connections.
A second more costly possibility is to buy a dryer cable, which is readily available and then cut the leads and connect it to a box with a 240v, 20 A outlet. Finally, connect the 240V, 20A plug on the extension box into that outlet.
I tried some searches online with words: electric, plug and 1030R in various combinations but almost always had chaff.
Help appreciated.
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