I made some! Here's the most common one:

<div class="rounded d-inline-block" style="background-image:linear-gradient(#ff85c0,#ff85c0 33.3%,#fff098 33.3%,#fff098 66.6%,#99dbff 66.6%);line-height:20px;width:26px;"><div style="background:url(https://files.catbox.moe/qufhp9.png) no-repeat center;background-size:60%;">&nbsp;</div></div>

And here's some other panromantic flags:

<div class="rounded d-inline-block" style="background-image:linear-gradient(#ff218c,#ff218c 33.3%,#fed800 33.3%,#fed800 66.6%,#21b1ff 66.6%);line-height:20px;width:26px;"><div style="background:url(https://files.catbox.moe/rx11j7.png) no-repeat center;background-size:60%;">&nbsp;</div></div>

<div class="rounded d-inline-block" style="background-image:linear-gradient(#0BA9F4,#0BA9F4 25%,#86CE00 25%,#86CE00 50%,#FF9826 50%,#FF9826 75%,#FF2662 75%);line-height:20px;width:26px;">&nbsp;</div>

<div class="rounded d-inline-block" style="background-image:linear-gradient(#D53973,#D53973 33.3%,#FF9776 33.3%,#FF9776 66.6%,#A962B2 66.6%);line-height:20px;width:26px;"><div class="d-inline-block" style="background-image:linear-gradient(#ff218c,#ff218c 33.3%,#fed800 33.3%,#fed800 66.6%,#21b1ff 66.6%);height:100%;clip-path:polygon(40% 0,60% 0,60% 100%,40% 100%);width:100%;">&nbsp;</div></div>