Normally you can add regex or xpath requests to the Spider to get the values. If they needs to be adjusted depending on the external url html structure, then it would be better to only extract the URLs then run regex/xpath formulas afterwards.
In the spider, you can uncheck "ignore external urls" and then use the Include button and add trustedshops. This will produce urls from all domains belonging to trustedshops.
I noticed a bug in the Spider which needs to be fixed. Unfortunately it looks like it can't process the external urls (same site, different domain).