There are hdmi mods for basically all pre hdmi consoles including n64 but they tend to be fairly pricey

N64 has pixelfx retrogem which has 2 models for 100 and 190 dollars, the more expensive model has 4k and additional scalers, the cheaper model is 720p

N64advanced v2 is open source, 4k output, and pricing depends on the group buy you can get in, 150-250

Highspeedido is on AliExpress, 720p output, and is 40-50

There’s also a few that aren’t sold anymore that you can sometimes find on ebay for $$$