Original by Markus Kuhn, adapted for HTML by Martin Dürst.

Keyboard Symbols with combining enclosing keycap

2380 20E3 ⎀⃣
2381 20E3 ⎁⃣
2382 20E3 ⎂⃣
2383 20E3 ⎃⃣
2384 20E3 ⎄⃣
2385 20E3 ⎅⃣
2386 20E3 ⎆⃣
2387 20E3 ⎇⃣
2388 20E3 ⎈⃣
2389 20E3 ⎉⃣
238A 20E3 ⎊⃣
238B 20E3 ⎋⃣
238C 20E3 ⎌⃣
2396 20E3 ⎖⃣
2397 20E3 ⎗⃣
2398 20E3 ⎘⃣
2399 20E3 ⎙⃣
239A 20E3 ⎚⃣

Information source with combining enclosing circle

2139 20DD ℹ⃝

All these are not expected to work in the normal half-width fonts, but
they should look reasonably good in the square full-width fonts.