One of the biggest contributing factors of urinary tract problems is cats not drinking enough water. Hence ur vet suggesting wet food as opposed to dry.
U can get some dry foods with added cranberry to boost the acid leval of the urine and make it less alkaline.
U could have a word with ur vet regarding a vit c supplement in pill form or using a product (in capsule form) called urieaze by vetplus which helps maintain urinary tract health.
One of the best products to try is a drinking fountain for cats....it really does get them drinking more, most seem to pref drinking running water and if u can increase the hydration levels then the urine is much more dilliute and less urinary tract infections!