Needham's Electronics
Formerly Dataman?
Notable for letting set programming voltage
https://www.docentelectronics.com/httpdocs/Needham/needham_electronics.htm
EMP-20
seems pretty popular, but parallel interface
http://ps-2.kev009.com/ohlandl/Needham_EMP20/EMP-20_Programmer.html
EMP-21
USB
EMP-20 vs EMP-21 - https://twitter.com/johndmcmaster/status/1152975472302575616 - Doesn't support voltage level tweaking -Doesn't support 8048
EMP-100
USB interface