If you want to get the real SARMS, they should only come in the form of a research chem suspended in liquid. If you get offered some pills or caps claiming that those are SARMS, beware, because these are 100% fakes. Real SARMS are only liquid.
I would recommend for your cycle to use Cardarine @ 12.5 mgs ED, Ostarine @ 25 mgs per day, Andarine S4 @ 50 mgs per day, and Nutrabol MK-677 @ 25 mgs per day. This, in my opinion, will be the perfect stack for a tennis player - good recovery, not much mass, and good joint healing properties. Use them for 12 weeks, and then do a 4 week mini-PCT consisting of nolvadex, clomid, Ostarine, and some good natty test booster. If you will want to run another cycle, and I am sure you will, wait 4 weeks after the PCT.
Regarding the source, go to the source section - there you will find a lot of information about different suppliers, and feedback from their customers.