For privacy reasons the official list of merit sources is not publicly available, we wouldn't want users bugging the sources for merits or scrutinizing their merit awarding.
There is NOTHING PRIVATE about this. Absolutely. Such a list of active sources can be made easily and simply. Just go to BPIP, go to the SENT rating tab and see the users who distributed more merit than they earned. This is sors. I myself can make such a table in a day and there will be nothing extra secret in it.