I have upgraded several family computers and have their older monitors for sale at $10 each. A power cord is included with each.
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AOC 1649fwu (1366 x 768; USB) [2 available]
This small monitor is very portable and is commonly used as an extended display for a laptop computer (in either landscape or portrait orientation). It uses a USB cable (included) for both power and data, so it does not need a power brick. Because it does not use the host computer's display connection (such as HDMI or DisplayPort), it requires installation of the DisplayLink Manager software for connectivity. This free software is available at displaylink.com. Windows, MacOS, and Ubuntu Linux are supported. (Photos show it in use with a MacBook Air.)
Specifications: https://www.bhphotovideo.com/c/product/830576-REG/Aoc_E1649FWU_E1649FWU_16_LCD_LED.html
User Manual: https://www.bhphotovideo.com/lit_files/70351.pdf
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Dell S199WFP (1440 x 900; Display Port, HDMI adapter included)
This is a compact 19" monitor suitable for a small desk.
Specifications: https://www.ascendtech.com/products/dell-19-s199wfpf-widescreen-lcd-monitor/m19dels199wfpfw
User Manual: https://dl.dell.com/manuals/all-products/esuprt_electronics/esuprt_display/dell-s199wfp_user%27s%20guide_en-us.pdf
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NEC Multisync EA234WMi (1960 x 1080; HDMI, Display Port)
This monitor has height adjustment, can be used in either landscape or portrait orientation, has a built-in USB hub for connecting peripherals, and has built-in speakers. (You can plug in a streaming device such as an Amazon FireTV Stick and use it as a television.) It has a couple of very minor pixel defects (see photo).
Specifications: https://www.displayspecifications.com/en/model/6d003e2
User Manual: https://www.manualslib.com/products/Nec-Multisync-Ea234wmi-4259866.html
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Samsung P2450 (1960 x 1080; HDMI, Display Port)
Specifications: https://www.bhphotovideo.com/c/product/687877-REG/Samsung_P2450H_SyncMaster_P2450H_24_Widescreen.html/specs
User Manual: https://www.manua.ls/samsung/p2450h/manual