Have you considered a Windows laptop?
I occasionally check eBay UK, eBay USA and eBay Australia
Here’s one like mine –
£250 (about AUD $460 + Postage and !0% import duties) - LENOVO THINKPAD W520 i7 Quad, 16gb RAM, 500gb Samsung EVO SSD
https://www.ebay.co.uk/itm/144092555...4AAOSwBvBg2efH
USA eBay often has Lenovo WE520s for US$200 to $300 with 16GB RAM
My W520 (model 427637U) can hold 4 @ 8GB RAM (as albeee1952/Dave mentioned, the RAM must be identical)
eBay Caveat:
Look for Sellers with lots of Sales a high % eBay Feedback
Ask questions before purchase and keep a Screenshot of the Seller’s reply, that includes both date and time
Pay via PayPal (costs slightly more) – because PayPal will arrange a Refund if you don’t get “what was advertised”
Refunds can take 2 to 3 months – and Buyer must pay the Return Postage
Good luck!