Digitech Jam-man is good, and TC Electronics Ditto is excellent, sonically. If you're looking to use it on gigs, Digitech is better, but for practice or home use, almost any brand will do. I found 'Boss loopers slightly noisy.
Lester Devoe Flamenco Negra
Lester Devoe Flamenco Blanca
Aparicio Flamenco Blanca with RMC pickup
Bartolex 7-string with RMC pickup
Giannini 7-string with Shadow pickup
Sal Pace 7-string archtop