hi,
Yes, erdport-datasets may be the easiest way to get to the data.
If you look at the table description, this table holds the ‘raw’ return, the size decile assignment, and the decile return:
http://wrds-web.wharton.upenn.edu/wrds/tools/variable.cfm?library_id=20&file_id=67324
This dataset seems reachable with the web interface to download datasets. Select CRSP, then Stock / Portfolio Assignments and then Capitalization Deciles.
You can also navigate the wrds directory structure with SSH (open source), and download SAS datasets to your computer and then convert it to Stata format with Stat Transfer.
The drawback of erdport-datasets is that there are observations that seem to be missing. (At least when I used them some time ago) So, constructing it yourself could get you a larger sample. Time-wise it is probably better to go with erdport-datasets.
I don’t know about the size decile data on French’s website. Obviously, the guy has a huge reputation, so it must be good 
best regards,
Joost