Something like this would be good and small form factor
HP EliteDesk 800 G2 Business Class Desktop, Intel Core i5 6500 3.2Ghz, 8GB DDR4 RAM, 256GB SSD Hard Drive, Windows 10 (Renewed) https://www.amazon.com/dp/B07M5B4VZ8/ref=cm_sw_r_cp_api_glt_fabc_DQV6A3MD28797AP2X3BB
As long as you mount...