I have a vanity sink chest 16" wide in interior and 40" long exterior. Is there a sink that will fit & still give enough size for everyday use?

The best I am coming up with are rectangular undermounts with exteriors of 21 1/4 x 15 /4 or 20 7/8 x 14 3/8. Would there be room to install an undermount this size, and still have room for a faucet?

If not, is there any kind of drop in or self rimming sink that you know if that might work?

TIA for all advice.

MBM