depending on the size you want it a 7" inch reverse monitor can work or you could go with a 5" inch getting a low powered( draws small amount of amps and possible 5v would be best.). your gonna need a case, screen,batteries,soldering iron, wire,solder, cooling fan depending, battery management system, charger for batteries, audio amp, speakers, screw drivers, tact switch, freemcboot(dvd drive draws to much),memory card,multimeter depending, breadboard if you want to mount certain things for more stability. some parts you can find on amazon, ebay, aliexpress etc. to me its best to wire both set of memory cards internally!
Screen(5" possible to run off 5v from reviews planning on getting one soon also!) :
https://www.amazon.com/gp/product/B...4df-15aac5223b10&pf_rd_r=MMRBH6ED6BJV5J0T5ZF4
case: can 3d print ,frankencase or buy a enclosure from polycase or so.
batteries I got mines (18650 cells) from old laptop battery packs. for the unit your going to need a 3s bms.
cooling fans im planning on using (bought already):
https://www.amazon.com/dp/B0792BW2V...colid=A2B4HI7KJWKV&psc=0&ref_=lv_ov_lig_dp_it
audio amp board(I use):
https://www.amazon.com/dp/B00LODGV6...colid=A2B4HI7KJWKV&psc=0&ref_=lv_ov_lig_dp_it
speakers :
https://www.amazon.com/dp/B07DVDW8P...colid=A2B4HI7KJWKV&psc=0&ref_=lv_ov_lig_dp_it