I will suggest not confining your covers to just isolated vocals. Signature riffs and licks are abundant and easily downloaded as well. Here is a YouTube link to Don Felder giving a lesson on all of his licks, solos and riffs for Hotel California. He has transposed the song to Am, which is likely a better key for a lot of voices than the original key. Don is very solid on his timing as well and this makes a very authentic cover as all the signature licks are there. Plus, Don Felder is your session musician along with all of the great PGMusic session musicians. A true All Star Band.
Don Felder Hotel California Guitar Lesson A tip to quickly get isolated vocals or other stems into BIAB or RB is to download the original song and run it through the ACW for the chord chart and an accurate tempo map in the original key. That will also give you a good guide for inserting the vocals into the BIAB backing track.
Some prolific singers on YouTube I've found that perform useable vocal/guitar songs are Alan Robinson, Austin Criswell and Larry L. (Podline66). Search for Larry L's early works that were done before he began to do a lot of post producing himself on his songs. Alan Robinson does tutorials but at the beginning of each lesson, records a complete performance of the song. Austin Criswell, I think, is a brilliant singer.
There are also many American Idol, America's Got Talent and The Voice performers who upload covers and originals with simple guitar or piano accompaniment that will have excellent vocal performances.
Charlie