I made an update for 1.21 (resource pack)

[Sovlus]

Simply replace the "playerhead" file in the 'font' folder of the resource pack with this:
{
"providers": [
{
"type": "space",
"advances": {
"\uF101": -1,
"\uF102": -2,
"\uF103": -3,
"\uF104": -4,
"\uF105": -5,
"\uF106": -6,
"\uF107": -7,
"\uF108": -8,
"\uF109": -9
}
},
{
"type": "bitmap",
"file": "minecraft:pixel1.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF001"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel2.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF002"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel3.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF003"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel4.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF004"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel5.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF005"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel6.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF006"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel7.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF007"
]
},
{
"type": "bitmap",
"file": "minecraft:pixel8.png",
"ascent": 8,
"height": 8,
"characters": [
"\uF008"
]
}
]
}