While you can't filter for topic properties and using the basic Find feature doesn't work either, you can search for them. Just click on the Find and Search button next to the Find box and a drop-down menu will appear. Under Search for All Occurrences, select either Search or Search in Current Map (unless you want to search multiple maps).
The Search task pane should appear (and if you have the task pane tabs visible you can click on the Search tabs to go directly to this pane). Click on More search options (in faint blue print under the Search button) and should see a selection of tick boxes for various options, including Topic property names and Topic property values.
The annoying thing is that there visible indication of the search results in the map they are not filtered or even highlighted. Instead the selected topics are listed under the current map name in the Search Results list that makes up the bottom half of the pane; clicking on an individual topic will highlight it on the map and you can also send the results to a selected topic or a new map, but that's about all you can do.
It would be great if the ability to filter properly for topic properties was built-in or even if the search function just had the option to highlight or the relevant topics in the map. In the short term it might be an idea to approach Nigel Goult at Olympic Limited to see if a future version of his MAP add-in for MindManager could incorporate at least the ability to highlight all the topics with properties that meet the search criteria.