What is a`reasonable time to wait for your solicitor to find a debtor?

Stalking isn't relevant when you've got a perfectly good reason for needing to stay in contact with someone (i.e. they owe you money) especially if they've made themselves scare with a view to not paying you. Your solicitor seems to be ripping you off - usually these people can be found on a results only basis - i.e. you only pay if they produce some positive evidence of the debtor's whereabouts. If you've got some positive means of contacting the debtor then p it on to your solicitor. Your solicitor should know how to turn such a contact into a promise to repay you which can be actioned in the court in the event you don't get your money back.