Where can I find a Detailed Surface Scanner in Elite Dangerous?
Solution 1:
Equipment searching can be tedious in Elite regardless of what equipment you are looking for.
There is no specific trick to finding a Detailed Surface Scanner, just generic advice for whenever you are searching for a particular piece of equipment.
Better equipment choice can be found in High Tech or Industrial systems. On the galaxy map, you can set a filter type to only show those sorts of planets. Wealthy systems with higher populations seem to give the widest choice - you can also set a filter to remove lower population systems.
When you've found a system that looks like a good candidate, look at the System Map and click on each of its stations. Check that they have Outfitting and also that their economies are High Tech or Industrial as it is possible to have a station with an Agricultural economy mixed in to a system with mostly High Tech economies (it seems to be based more around the planet that the station is orbiting).
Even after doing this, the stock at the stations is randomised and will change over time, so they might have one the first time you check, but it not be there when you have saved up enough to buy one.
If you are anywhere near Xihe, check that place out. It is my first stop shop for equipment - it always seemed to have everything you need to fully upgrade the smaller ships up to a Cobra Mk 3.
Solution 2:
As others have mentioned, the wiki lists locations that sell the detailed surface scanner. I offer another, more generic solution, in the form of EDDB.
EDDB is the Swiss Army Knife to any commander.
For instance, to find the detailed surface scanner nearest to your location, click on the "Stations" tab.
In the field "Stations sells Modules" type "Det" and it should auto-complete to the detailed surface scanner.
Next, enter the system (not the station) where you find yourself into the "Reference System" box. Example: I am currently at Ohm station in LHS 20, so I enter "LHS 20" for my reference system.
Tip: It lists in between brackets the station names that are in that system. Check your current station is in that list. If not, then you may have mistyped your system. Some systems have very cryptic, coded designations that closely match other systems and so can easily be mistyped.
Finally click the "Find Stations" button and wait for the results to come back. The results are sorted on distance (shortest to longest) from your system and will include the station name where you need to dock or land. It does not list the price however.
Use the same website for finding other parts.
You can also use EDDB for trading and other purposes, but now we're veering OT. If interested in these other services, hit your favourite search engine.