I use a 21 hole Japanese " TOMBO " brand. Other models vary between 16 & 30 holes, & I am afraid they are not cheap----mine cost 67 pounds !! But the octaves are "full" ,so you can play the same tunes that you could on a tin-whistle. Also,being Japanese,they are extremely well made,& have a lovely tone.At that price,you probably won"t want a box-full of "em, so I guess one in the key of G should suffice for most pub-type "sessions ". But if other keys are your bag, well,my Tombo (it"s called a "Band" model) is available in 12 major,12 minor, & 12 natural minor keys.And they don"t fall apart after a month !! I bought mine from " The Music Room" in Oxford . Tombo"s website is www.tombo-m.co.jp    ----Go for it !!!