I bought an Imsai8080 replica from https://thehighnibble.com/imsai8080/
I had a really nice time building the kit, toggle switches and display leds look exactly like original ones. Internally is an emulation of the IMSAI 8080 based on the ESP32 microcontroller
You may also find a more faithful replica of the Altair 8800 here https://altairclone.com/ though admittedly the IMSAI with its big coloured toggles is much more eye-catching.
There's also a very affordable (< $100, including the needed Arduino DUE) workalike that pops up on eBay every now and again...I bought one: https://imgur.com/a/qntqSMG
Basically have fun playing around with it in the same way as with a real IMSAI8080... As an example look at this video on how to enter and run a small assembler program using the switches. https://www.youtube.com/watch?v=xYNAMKPBSFI