I just put a set of these 27 x 1-1/4" Schwalbe Marathons on my Shogun touring bike. Got a great deal on them at planetcyclery on ebay last fall. About $65 for the pair incl. shipping.
(link: https://www.ebay.com/usr/planetcyclery?ul_noapp=true ). Only thing about them is they're real heavy items. Have had to pump them all the way up to the maximum rating of 95psi to get them to roll fast. But, if it helps prevent flats then that's OK with me.